Ventilator system with removable airway

ABSTRACT

The present disclosure provides techniques for a ventilator system with a removable airway. A ventilator system may include a removable airway and a base unit. The removable airway may include an air inlet port, a patient inhalation port, an air exhaust port, and a patient exhalation port. The base unit may include two pinch valves. In some cases, the removable airway does not comprise any openings other than the air inlet port, the air exhaust port, the patient inhalation port, and the patient exhalation port. In some cases, the removable airway is configured such that air inside the removable airway does not contact any part of the base unit. In some cases, the removable airway is configured such that air that enters the patient exhalation port is contained within the removable airway along a contiguous path and at no point does the contiguous path contact the base unit.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/241,248, filed on Apr. 27, 2021, and entitled “Ventilator System WithRemovable Airway,” which claims priority to: 1) U.S. Provisional PatentApplication No. 63/016,995, filed on Apr. 29, 2020, and entitled“Ventilator”; 2) U.S. Provisional Patent Application No. 63/086,055,filed on Oct. 1, 2020, and entitled “Ventilator with Removable Airway”;and 3) U.S. Provisional Patent Application No. 63/086,375, filed on Oct.1, 2020, and entitled “Ventilator with Removable Airway”; all of whichare hereby incorporated by reference for all purposes.

BACKGROUND

A ventilator is a machine that provides mechanical ventilation by movingbreathable air into and out of the lungs of a patient, for example, todeliver breaths to a patient who is physically unable to breathe, or isbreathing insufficiently. Conventional ventilators may be machines withvalves controlled by a computerized (e.g., microprocessor-controlled)control system based on the feedback of sensors (e.g., pressure and flowsensors), or may be more basic machines (e.g., containing ahand-operated bag, a valve, and a mask). Ventilators are typically usedin intensive-care medicine, home care, emergency medicine, and inanesthesiology (as a component of an anesthesia machine).

There are different types of conventional ventilators, such as volumeventilators and pressure-cycled ventilators. Conventional ventilatorsare susceptible to contamination, for example, from a patient coupled tothe ventilator. The interior surfaces of the ventilator, includingvalves and sensors, are exposed to air exhaled from a patient. The airfrom a patient may contain pathogens, such as bacteria associated withnosocomial pneumonia, which can contaminate the ventilator andpotentially infect a subsequent user of the ventilator (e.g., the nextpatient to use the ventilator). Some components of conventionalventilators may be cleaned or replaced between use by differentpatients, however, cleaning or replacing some components is ineffectiveif other adjoining regions within the ventilator remain contaminated.For example, bacteria that remains in some areas of a ventilator (e.g.,a moving component of a valve, or a surface of a pressure or flowsensor) may contaminate the air stream moving through the ventilator,thereby contaminating the rest of the system.

SUMMARY

The present disclosure provides techniques for a ventilator system witha removable airway. In some embodiments, a ventilator system comprises aremovable airway and a base unit. The removable airway can comprise: anair inlet port; a patient inhalation port; an air exhaust port; and apatient exhalation port. The base unit can comprise two pinch valves.The removable airway is configured such that air can enter the removableairway through the air inlet port, be exhausted from the removableairway through the air exhaust port, leave the removable airway throughthe patient inhalation port, and enter the removable airway through thepatient exhalation port. In some cases, the removable airway does notcomprise any openings other than the air inlet port, the air exhaustport, the patient inhalation port, and the patient exhalation port. Insome cases, the removable airway is configured such that air within theremovable airway does not contact any part of the base unit.

In some embodiments, a ventilator system comprises a removable airwayand a base unit. The removable airway can comprise: an air inlet port; apatient inhalation port; an air exhaust port; and a patient exhalationport. The base unit can comprise two pinch valves. The removable airwayis configured such that air can enter the removable airway through theair inlet port, be exhausted from the removable airway through the airexhaust port, leave the removable airway through the patient inhalationport, and enter the removable airway through the patient exhalationport. In some cases, the removable airway is configured such that airthat enters the patient exhalation port is contained within theremovable airway along a contiguous path and at no point does thecontiguous path contact the base unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic of an example of an inhale manifold ofa ventilator system, in accordance with some embodiments.

FIG. 2 is a simplified schematic of an example of an exhale manifold ofa ventilator system, in accordance with some embodiments.

FIGS. 3A and 3B are simplified schematics of an example of a pinchvalve, in accordance with some embodiments.

FIGS. 4A and 4B are simplified schematics of another example of a pinchvalve, in accordance with some embodiments.

FIG. 5 is a simplified schematic of the pinch valve shown in FIGS. 4Aand 4B, in accordance with some embodiments.

FIGS. 6A and 6B are simplified schematics, in front view and side view,respectively, of an example of a system for controlling the position ofa valve, in accordance with some embodiments.

FIG. 7 is a simplified schematic of an example of a system forcontrolling the position of a valve, in accordance with someembodiments.

FIG. 8 is a simplified schematic showing an example of pressure-limitingand pressure-limit detection subsystem, in accordance with someembodiments.

FIG. 9 is a simplified schematic showing an example of a pressure limitdetection subsystem, in accordance with some embodiments.

FIGS. 10-12 are simplified schematics of examples of bellows, inaccordance with some embodiments.

FIGS. 13A-13C are simplified schematics of an example of a pressuredetection system, in accordance with some embodiments.

FIG. 14 is a simplified schematic of an example of a flow sensor, inaccordance with some embodiments.

FIG. 15 is a simplified schematic of an example of a complete gasmanifold (e.g., airway) of a ventilator system, in accordance with someembodiments.

FIG. 16 is a simplified schematic of an example of the complete gasmanifold in FIG. 15, including portions of the sensors in the manifold(e.g., airway) and the electric eye portions of the sensors located inthe ventilator base unit, in accordance with some embodiments.

FIGS. 17A-17B are simplified schematics of examples of electric eyes, inaccordance with some embodiments.

FIG. 18 is a simplified schematic of an example of a ventilator system,in accordance with some embodiments.

FIG. 19 is a simplified schematic of an example of a ventilator system,in accordance with some embodiments.

FIG. 20 is a simplified schematic of an example of a sensor withportions in the removable system and in the base unit, in accordancewith some embodiments.

FIGS. 21A-21B are simplified schematics of an example of an airway witha compliant region, in accordance with some embodiments.

FIGS. 22A-22B are simplified schematics of an example of a pressuresensor, in accordance with some embodiments.

FIGS. 23A-23B are simplified schematics of an example of a pressuresensor, in accordance with some embodiments.

FIG. 24 is a simplified schematic of an example of a flow sensorcontained within the base unit, in accordance with some embodiments.

FIG. 25 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system and that are part of thebase unit, in accordance with some embodiments.

FIG. 26 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system and that are part of thebase unit, in accordance with some embodiments.

FIG. 27 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system and that are part of thebase unit, in accordance with some embodiments.

FIG. 28 is a simplified schematic of an example of a flow sensor that iscontained within the removable system, in accordance with someembodiments.

FIG. 29 is a simplified schematic of a flow sensor that is a part of theremovable system, or with portions that are part of the removable systemand the base unit, in accordance with some embodiments.

FIG. 30 shows a simplified schematic of an example of a structure withina tube that may generate sound that can be detected by a microphone of aflow sensor, and the frequency spectrum of the sound that is processedto determine a flow rate of the gas (e.g., air), in accordance with someembodiments.

FIGS. 31A-31B are simplified schematics of a flow sensor with portionsthat are part of the removable system and the base unit, in accordancewith some embodiments.

FIG. 32 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system and the base unit, inaccordance with some embodiments.

FIGS. 33A-33E are simplified schematics of portions of flow sensors thatmay be used in flow sensors that are contained in the removable system,or that have portions that are part of the removable system and the baseunit, in accordance with some embodiments.

FIGS. 34A-34C are simplified schematics of an example of a ventilatorsystem with a removable airway, in accordance with some embodiments.

FIGS. 35A-35B are simplified schematics of examples of an inhale lineand an exhale line, respectively, of a ventilator system, in accordancewith some embodiments.

DETAILED DESCRIPTION

A ventilator system is disclosed for supporting breathing in a human orother animal, such as a primate. The ventilator system may contain aremovable unit and a base unit, where the removable unit may also bedisposable.

In some cases, the removable unit can be removed from the base unitmanually (e.g., using a person's hands only). In some cases, theremovable unit can be removed from the base unit without using any tools(e.g., without using a screwdriver, or pliers, or any other tools). Insome cases, the removable unit can be removed from the base unit with atool (e.g., a screwdriver), wherein the number of operations required toremove the removable unit is minimal, such as from 1 to 4 operations(e.g., where the 1 to 4 operations comprise removing 1 to 4 screws). Insome cases, the removable unit may be removed and disposed ofperiodically (e.g., between use of the ventilator by different patients,or after a particular time duration, such as daily or weekly).

In some cases, all of the air exhaled from a patient coupled to theventilator (e.g., through a patient circuit, and/or endotracheal tube)is constrained to move within the removable unit (e.g., a removableairway), and/or none of the air exhaled from the patient may contact thebase unit. In some cases, the air exhaled from the patient passesthrough the removable unit, without contacting the base unit, and thenair is expelled from a port of the removable unit (e.g., through afilter) into the atmosphere wherein it may contact some portions (e.g.,exterior surfaces) of the base unit. Cross-contamination betweenpatients can be eliminated (or mitigated, or reduced) using theventilators described herein, which include a removable unit (e.g.,airway) that 1) may be removed and replaced between patients, and 2)that prevents air (and other materials or particles) exhaled from thepatient from contacting any part of the ventilator other than theremovable unit (e.g., from contacting any part of the base unit).

The air in the ventilator systems described herein may contain oxygen,nitrogen, other gases, other materials (such as liquid particles, solidparticles, pathogens, and/or medicinal aerosols), and mixtures thereof.

In some embodiments, the ventilator systems described herein includevalves to control the flow of air through the removable unit. The valvescan include moving parts to reduce the flow through a portion (e.g., atube) of the removable unit. In some cases, no moving parts of thevalves come into contact with air exhaled from a patient that is coupledto the ventilators described herein. For example, a valve can contain amoving element and a fixed element, where the moving element isconfigured to compress a tube of the removable unit (where the tube ispositioned between the movable and the fixed element) therebyrestricting flow through the tube in a controlled manner.

In some embodiments, the removable airway system may contain a one-wayvalve that opens at a preset pressure, such as a blow-off valve. Thepreset pressure may be set at a level that protects the lungs fromoverpressure, such as 50 or 60 cmH₂O. The base unit may have a subsystemfor detection of an overpressure event such as detecting motion of thevalve or flow from the valve.

In some embodiments, the ventilator systems described herein includesensors (e.g., pressure sensors, flow sensors, and temperature sensors).In some cases, the sensor is contained in the base unit, such that nopart of the sensor can come into contact with air exhaled from a patientthat is coupled to the ventilators described herein. In otherembodiments, the sensor is contained within the removable unit, and mayhave electrical connections (e.g., wires) that penetrate a portion(e.g., a tube) of the removable unit (e.g., through sealed openings thatdo not allow air from the removable unit to escape through). In otherembodiments, the sensors have a portion in the removable unit and aportion in the base unit, wherein the portion in the removable unit maycome into contact with air exhaled from a patient that is coupled to theventilator, and the portion in the base unit cannot come into contactwith air exhaled from a patient that is coupled to the ventilator. Forexample, a pressure sensor can contain a compliant region (e.g.,disposed on a surface of a tube) of the removable unit, and a load celladjacent to the compliant region in the base unit, such that pressurechanges within the removable unit create changes in a force on thecompliant region thereby causing the compliant region to move and theload cell to detect the force (and/or movement) of the compliant region.In this example, the compliant region would be exposed to air exhaledfrom a patient, but the load cell would not come into contact with airexhaled from the patient. Such sensors can be cost effective, sinceinexpensive portions can be located within the removable unit (e.g., tobe disposed of after use by a patient, before the ventilator is used bya different patient), while the more expensive portions (e.g., the loadcell in this example) can be protected from contamination and thereforebe used many times (e.g., by different patients).

In some cases, the complexity of the removable unit is minimized, forexample, to minimize cost of a potentially disposable removable unit.

In some embodiments, the ventilator includes: 1) an airway manifold(i.e., removable airway) that is removable (and in some cases is alsodisposable), where the removable airway may transfer air exhaled from apatient coupled to the ventilator to a filtered exhaust; 2) a baseventilator unit, where the removable airway and the base unit areconfigured such that no air from a patient touches any components of thebase ventilator unit; 3) valves, including valve components that no airfrom a patient touches (e.g., using a moving element to compress a tubeof the removable airway); 4) pressure sensors that are configured withpressure sensor components that no air from a patient touches (e.g.,using a compliant component in the airway and a pressure sensorcomponent outside the airway that no air from a patient touches, orwater-based sensors); 5) flow sensors that are configured with flowsensor components that no air from a patient touches (e.g., using adiaphragm component in the airway and a flow sensor component outsidethe airway that no air from a patient touches); and/or 6) a controlsystem coupled to the valves, that may also be coupled to the sensors,where the control system controls the opening and closing of the valvesto control the flow of air through the removable airway. In some cases,a measurement of pressure or flow or volume within the removable airwayis converted to an electrical signal via an electric eye.

In some embodiments, the ventilator system is comprised of pressure andflow controlling subsystems (e.g., valves) and measurement components(e.g., sensors). The removable unit (or airway) of the ventilatorsystems described herein may include an air manifold for incoming air toa patient (i.e., an inhale manifold), and a manifold for air leaving apatient (i.e., an exhale manifold).

The ventilator systems described herein may also include a controlsystem for opening and closing of valves. The control system may becoupled to one or more valves of the ventilator system to control theopening and closing of the valves. The control system may be coupled toone or more sensors, and may be configured to receive signals from thesensors, process the signals into information, and use the informationto control one or more components (e.g., one or more valves) of thesystem. The processor may communicate with the one or more valves,and/or with the one or more sensors, through a bus system. The controlsystem may contain a processor (or microprocessor), and may containnon-transitory computer readable memory coupled to the processor (e.g.,through a bus system).

In some cases, the electronics of the system may have no microprocessor.In some cases, all functions may be hard-wired into an analog and/ordigital circuit, such that the system has no software. This can bebeneficial for safety testing and development cost.

In some embodiments, the removable unit of the ventilators describedherein includes connections for air in and air out, and connections to apatient for inhale and exhale lines (e.g., of a patient circuit and/orendotracheal tube). The air that passes through the removable unit mayhave no pathway, connection, or contact to any part of the baseventilator unit. The air from a patient connected to the ventilatorsystem may not contact any of the base unit. In some cases, the air froma patient connected to the ventilator system may not contact any of thebase unit without passing through an exhaust port, which may befiltered. That is, there may be no pathway through open conduits fromthe airway of a patient connected to the ventilator system and the baseunit. In some cases, there may be no pathway through open conduits fromthe airway of a patient connected to the ventilator system and the baseunit that are not filtered exhaust ports. Again, the air or any otherparticle or matter that can come into the ventilator from tubes or othermeans connecting to a patient is completely isolated from the rest ofthe ventilator, meaning there is no way for the air or matter to reachand contact surfaces of the ventilator outside of the removable parts.In some cases, the air or any other particle or matter that can comeinto the ventilator from tubes or other means connecting to a patient iscompletely isolated from the rest of the ventilator, and there is no wayfor the air or matter to reach and contact surfaces of the ventilatoroutside of the removable parts, other than by exiting an exhaust portfirst. Regions or surfaces of the base unit that are not intended to bein contact with air within the removable unit are considered outside ofthe removable unit. The base unit is a part of a ventilator system thatis other than the disposable unit or disposable system(s) orsubsystem(s).

In some cases, the air from a patient connected to the ventilator systemcontacts a first removable unit (airway), the patient is disconnectedfrom the ventilator system, and the first removable unit (airway) isremoved from the base unit and replaced with a second removable unit(airway). In such cases, the air from the patient may contact the firstremovable unit (airway), and air from the patient may contact a portionof the base unit, as long as any contamination on the portion of thebase unit cannot be introduced into the second removable unit (airway).For example, a patient may contaminate the first removable unit (airway)with bacteria, and the air from the patient may contact a portion of thebase unit thereby contaminating that portion of the base unit. However,the contamination from the portion of the base unit cannot contaminatethe second removable unit (airway) (e.g., due to positive pressuresecond within the removable airway). This case could arise in the casethat air from the first removable unit (airway) leaks and contaminatesthe base unit, however, there is no path for the contamination from thebase unit to reenter the first or enter the second removable unit(airway) (e.g., due to positive pressure within the second removableairway).

In some cases, air may leak from a connection between the ventilatorsystems described herein and a patient circuit, and that air couldpossibly contact a part of the base without exiting through an exhaustport (or a dedicated exhaust port). However, in such cases, air thatleaks from the patient connection is not air inside the removableairway.

In some cases, air or matter from a patient within the removable airwaypasses through one or more filters before leaving an exit port to theatmosphere. In some cases, air or matter from a patient within theremovable airway may only leave through one or more openings (e.g., anexit port, or a patient inhale circuit) and the one or more openings arededicated openings, wherein the dedicated opening is used to expelexcess gas from the airway (e.g., to the atmosphere, or to a patient)and the dedicated opening is not used for any other function (e.g., as asensor port). Additionally, in some cases, all of the valve componentsused to constrict flow within the removable airway are contained in thebase unit, and no valve components can contact the air (or mattercontained therein) that is exhaled from the patient. In other cases, theremovable unit may have one or more valve components that are portionsof the valve system, where the valve components may or may not contactthe air within the removable unit. In some cases, the valve componentscan be coupled to the outside or the inside of the tube of the removableunit that contains the air. For example, the removable unit may containa valve component that is in contact with the outside of a tube, wherethe valve component is a first portion of the valve. When such aremovable unit is inserted in the base unit, a second portion of thevalve in the base unit may push against the valve component (e.g., aplunger) of the first portion of the valve, and the valve component maypush against the tube rather than the valve in the base unit pushingagainst the tube directly.

In some cases, the incoming air that will be supplied to the patiententers the removable airway at a port. A valve may be disposeddownstream of the port. The incoming air has a pressure such that whenthe valve is opened, there is an airflow through the valve downstream,which prevents any matter that may be in the airway downstream of thevalve from moving upstream of the valve. In this manner, the source ofgas is protected from contamination by patient air or matter.

In some cases, a pathogen (e.g., bacteria) from the environment couldcontaminate a removable unit (airway) of the ventilator systemsdescribed herein, for example, by entering the removable unit through aninlet. The ventilator systems described herein are advantageous in suchsituations because the removable unit (airway) can be removedperiodically (e.g., between patients) thereby limiting the amount oftime the pathogen (e.g., bacteria) can grow within the removable unit(airway), and limiting the number of patients exposed to thecontamination.

In some cases, the airway is configured to be cleaned in place (e.g.,the airway may be configured to be removable and also configured to becleaned in place, or the airway may not be configured to be removable).The capability to be cleaned may be enabled by the isolation of theairway from the base unit. The systems described herein may be suitablefor cleaning due to the lack of tortuous paths and nooks and crannies(or regions which are tightly confined such as cracks or small tubes,where tight and small are defined with respect to the ability of acleaning agent to penetrate these regions). In some cases, the materialsof the airway are suitable for chemical, thermal, or UV sterilization.In some cases, the airway of the ventilators described herein isgenerally straight and contains no volume regions that are less than 10mm at their smallest dimension, or spaces that have dimensions (i.e.,interior dimension of the space) smaller than 5 mm. The above shapes andsizes of the airway can make the ventilator system described herein easyto clean. In some embodiments, a ventilator system described herein hasan isolated airway that is easily cleanable without the need to removeany parts of the system. To clean the ventilator systems describedherein sterilizing agent may be introducible by connection to thevarious inlets and outlets. Other sterilizing methods such as heat andultraviolet light may also be used to clean the ventilator systemsdescribed herein.

The ventilator systems described herein may include airways that areremovable from a base unit, and that may be removed to be cleaned or tobe disposed of If disposed of, then they can be subsequently replacedwith a new unit or a cleaned unit. In some embodiments, the isolatedairway is removable. In some embodiments, the removable airway isdisposable. In some embodiments, the removable airway is cleanable.These embodiments are not mutually exclusive.

In some embodiments, ventilator systems described herein include one ormore valves that compress a tube that passes through the valve. Suchvalves are commonly called “pinch” valves. In a pinch valve, the tubemay be removed from the valve. Pinch valves have the preferred advantagethat no fluid from inside the tube touches the valve components. Thus,no sterilization of the valve is needed between uses if the tube isremoved and disposed of and another tube is inserted into the valve. Insome cases, a pinch valve of a ventilator described herein has an openposition (or tube removal position) that allows insertion and removal ofthe tube. In some cases, the valve has an open position used duringoperation, and a tube removal position where the valve opens wider thanin the open position.

In some cases, the pinch valves of the ventilator systems describedherein may be configured to variably adjust the flow of gas through thevalve (i.e., through a tube passing through the valve, or through acompressible section of a tube passing through the valve). By varyingthe pressure on the tube that passes through the pinch valve, the amountof compression in a region of the tube may be varied from nocompression, to partially compressed, to fully compressed. When the tubehas no compression, the valve is in a fully open position, where theflow through the valve is maximal. When the region of the tube is fullycompressed, the cross-sectional area of an interior space of the tubewhere it is compressed is zero, so no air may pass through the tube, andthe valve is considered fully closed. In a partially compressedposition, the cross-sectional area of the interior space of the tube atthe region of compression is reduced compared to the fully openposition, resulting in higher flow resistance, with an associatedreduced flow when gas is passing through the valve. The moveablecomponent of the valve may in some cases have a continuously or nearlycontinuously adjustable range of positions which result in a continuousor nearly continuous range of cross-sectional areas of an interior spaceof the tube. In this manner, the flow rate of the pinch valve with atubing section of the removable airway passing through it may becontinuously or nearly continuously adjusted.

In some cases, a pinch valve of the ventilator systems described hereinthat can variably adjust the flow of gas through the valve, includes arotating arm that is controlled by a stepper motor to adjust the flowthrough the valve. The steps of the stepper motor may be miniscule, suchas 0.1 degrees per step, such that there is a minimum of adjustmentsize, where in some cases this minimum level of motion results inchanges of flow below the level of detection of flow sensors of thesystem. This case may be considered as an example of a valve that can benearly continuously adjusted.

A pinch valve of the ventilator systems described herein that canvariably adjust the flow of gas through the valve may also have a set ofpredetermined positions or settings such that the flow may be variedover a set of values, such as 0, ¼, ½, ¾ and 1 where these numberscorrespond to the fraction of flow through the valve compared to a fullflow through the valve.

A pinch valve of the ventilator systems described herein that canvariably adjust the flow of gas through the valve may be configured insome cases in either open loop or closed loop control. In open loopcontrol, the valve may be set at positions determined by predeterminedsettings, and not at positions determined as a result of sensorreadings. In closed loop control, the position of the valve is changedin response to a sensor reading, such as a flow sensor. In some cases,there is a continuing cycle wherein the sensor value is determined by acontrol system, and this sensor value (e.g., a flow rate) is compared toa setting value (e.g., a flow rate) that has been input to the controlsystem, and a difference is determined. This difference is then used toeither further open or close the valve in order to make the differencesmaller (i.e., to make the sensor value closer to the setting value).For example, if a measured flow is higher than an input setting, thenthe valve would be adjusted to a more closed position in response to themeasured flow value. After adjustment of the valve, the sensor may thenbe read again, and the valve further adjusted. The cycle may continueuntil the difference between the sensor reading and the input settingare the same within system tolerances or a preset minimum difference.The increments by which the valve is adjusted for each cycle may be setin a control algorithm, such as using a Proportional, Integral,Derivative (PID) control method. The control algorithm may also includeartificial intelligence (AI) wherein a position needed to achieve aparticular flow rate may be derived from a set of past data from aplurality of inputs of the system wherein the valve setting may belearned from the data set.

The ventilator systems disclosed herein may contain a device orsubsystem for the generation of a mixed gas with a particular fractionof inspired oxygen (FiO₂) (e.g., between about 0.2 and about 1.0, orbetween 0.21 and 0.5, or between 0.21 and 1.0) from pure oxygen. A gassource may be connected directly to an inlet port of the removable unit.The gas source be a mixed gas with a particular FiO₂. The source of thegas may be a pressurized line, a tank, or a compressor or blower. Thebase unit may have inlets for multiple gas sources, such as oxygen andnitrogen, and the base unit may have a subsystem for blending theseinlet gases, and an outlet that provides the mixed gases to the input ofthe removable unit.

In some cases, pinch valves with rotary elements for the ventilatorsystems herein can use motors with 30 RPM and a torque of 40 gram-cm.For example, such a motor can be used to compress a silicone tube (e.g.,with a ½″ diameter).

The removable unit (airway) may contain one or more tubes. The tubes inthe ventilator systems described herein may be of any flexible materialsuch as vinyl or silicone. In some cases, the tube can withstandmultiple (e.g., about 1 million, or from 100,000 to 2 million, or from100,000 to 10 million, or more than 1 million, or more than 10 million)compression (or inhale, or exhale) cycles. For example, breathing at 20breaths/minute for 10 days is 288,000 cycles. Vinyl and silicone areexamples of tubing material that can meet the requirements of theventilator systems described herein. In some cases, the tubing maycontain reinforcement fibers within or connected to the tubing walls,such that the tubing may withstand higher pressures than without thereinforcement fibers, yet remain compressible. In some cases, theremovable unit (or airway) may be made of low cost plastic materials sothat it is not costly to dispose of between patients.

The motor used by the valves in the ventilator systems described hereinmay be any motor capable of actuating the valve, or providing movementfor a component of the ventilator system such as a DC motor, a steppermotor, a servo motor, a controllable positionable motor, a linearactuator, or a positionable actuator. A control circuit may position themotor by turning it on and off. In some cases, the position of the motormay be determined by an electric eye, including a light emitter and alight sensor.

The removable system of the ventilators described herein may containsensors. Sensors may be for pressure, flow, and/or other parameters(e.g., temperature). The sensors may be active, such as powered byelectricity. If the removable system contains sensors, then theremovable system may have connectors on the removable system that mateto connectors on the base unit of the ventilators described herein. Theconnectors may be electrical. Electrical connections to sensors in theventilators described herein may also be non-contact. Power to thesensors may be wireless, such as using the Qi standard, or otherradiative or inductive means. Communication with the processor orcontrol system (e.g., from a sensor, and/or to a valve) of theventilators described herein may be wireless or wired, such as by WiFior Bluetooth.

The removable unit of the ventilators described herein may have regionsor systems that together with a related system in the base unit form asensor system. In some embodiments, the regions or systems in theremovable unit are passive, in that they do not contain any activecomponents, such as electronics or sensors that receive electricalpower.

In some cases, the ventilator systems described herein use electric eyescontaining an emitter and a detector configured to detect one or moreconditions within the system. The electric eyes disclosed herein may beconfigured with the emitter and the detector on either side of a(transparent, or translucent) region of interest (e.g., a tube). Inother cases, the emitter and detector can be configured such that lightfrom the emitter reflects off of a reflective surface, such as aretroreflective surface, or a high contrast light and dark surface, andis detected by the detector. For example, the emitter and the detectormay be facing generally the same direction and be close to, or within aproximity of, each other.

In some cases, the ventilator systems described herein have parametersthat are adjustable either electrically or mechanically. For example,the delays between cycles which are related to the inhale:exhale timeratio, may be adjusted by an input to a control system such as with aknob and a variable resistor. Peak inspiratory pressure (PIP) may beadjusted, for example, by moving a PIP pressure-limiting vessel up anddown, as described herein. The positive end expiratory pressure (PEEP)may be adjusted similarly, for example, by adjusting a PEEPpressure-limiting vessel up and down, as described herein. In somecases, the tidal volumes on inhale and exhale may be adjusted by movingan electric eye sensor up and down, as described herein. In some cases,the minimum flow detectable in the flow sensors may be adjusted bymoving an electric eye up and down, as described herein. In some cases,the triggered breathing pressure may be adjusted by a moving an electriceye sensor up and down, as described herein. In some cases, all of themechanical adjustments described above may include mechanisms thatattach the part to be moved to a slider on a panel that can be adjustedby user. For example, the panel may have 7 user-adjustable sliders, onefor each of the adjustments described above. In some cases, the panelalso has two knobs to adjust delays relating to breathing rate.

In some embodiments, the ventilator systems described herein include oneor more pressure-limiting subsystems, and/or one or morepressure-limiting and pressure-limit detection subsystems, containing aliquid (e.g., water or oil). In some cases, pressure-limiting subsystemsinclude a vessel containing a liquid (e.g., water or oil) and a tubesubmerged in the water, where the depth of the tube limits the pressurein the tube above the liquid in the vessel.). In some cases,pressure-limiting and pressure-limit detection subsystems include avessel containing a liquid (e.g., water or oil) and a tube submerged inthe water, where the depth of the tube limits the pressure in the tubeabove the liquid in the vessel, and where a detector (e.g., an electriceye) is used to determine if the pressure limit is exceeded (e.g., bydetecting bubbles in the liquid).

In some embodiments, a method for using a ventilator system describedherein includes the following steps. In some cases, an operator opens adoor, inserts a removable airway manifold, and fills it with water (oroil) in the correct places (e.g., in pressure-limiting subsystems). Thedoor may be located at the back of the unit opposite a control panel,where the control panel is coupled to movable sensors. The operator maythen close the door, and may attach the unit to a patient and a gassource. The ventilator may also include a means (as described above) forgenerating and adjusting a mixed gas with a particular FiO₂, such thatthe input gas (e.g., to an inhale line of the ventilator system) may bepure O₂ mixed with another gas (e.g., air, or nitrogen), and theoperator may open a valve (e.g., that is part of the ventilator system,or part of a system outside of the ventilator system) to introduce theinput gas into the system. In some cases, the ventilator system can becoupled to an air source (e.g., an air compressor, or a mixed gas (e.g.,FiO₂) generating system) using a self-sealing fitting, and no valvebetween the air source and the ventilator is needed. Thepressure-limiting subsystems (e.g., PIP and PEEP vessels, as describedherein) may also be connected to the rest of the system by the operator,such as via snapping them into one or more holders that are connected toa slider for adjustment up and down on the control panel.

In some cases, the ventilator systems described herein may include ascreen-type user interface (e.g., an LCD display). In some cases, theventilator system may include an LED-based user interface (e.g., with aset of LED indicators, or a set of LEDs forming a display). In someembodiments, the interface displays the sequencing of the valves, andflow, and other sensor data (e.g., from electric eyes). Patient data mayalso be stored and output by the control system.

In some embodiments, the ventilator systems described herein include oneor more flow sensors, one or more pressure sensors, and one or moretemperature sensors. The flow, pressure, and/or temperature sensors canhave portions in the removable unit (airway) and/or in the base unit.The temperature sensor may be non-contact, such as by using an infra-reddetector to determine the temperature of the air inside the airway.Non-contact temperature measurements can be taken, for example, througha window, or by detecting the surface temperature of a region or regionsof the airway as an indicator of the temperature inside the airway. Atemperature sensor may in some cases have a contact in the base unitthat comes in contact with a region or regions of the airway, where thecontact in the base unit may include a temperature sensor such as athermistor.

In some embodiments, active components of sensors (e.g., pressure andflow sensors) may be incorporated into the removable unit (or airway) ofthe ventilator systems described herein. For example, a heat source suchas a hot wire and a temperature sensor such as a thermistor may bedisposed in the airway, with external electrical connections to a matingpart on the base unit, to enable what is generally known as hot-wireanemometry. Pressure sensors such as MEMS sensors may also be disposedin the airway with external electrical connections that mate to a baseunit. The removable unit may contain a power source such as a battery,or have connections to a power source via a plug or contact-basedconnector, or have a wireless source of energy, such as by using a Qistandard. The removable unit may also include electronics (e.g., aprocessor to process measurements taken by one or more sensors, acommunication unit to wirelessly communicate with a communication unitand a processor in the base unit, and/or wireless power receiver(s)).The sensors in the removable unit may send (or communicate) ameasurement to the electronics in the removable unit, and optionallyinformation from the measurement may be transmitted wirelessly to thebase unit.

In some embodiments, the ventilator systems described herein include aflow sensor that can detect a flowing gas, or a flow rate of a gas,where the gas may contain other material (e.g., particles). The flowsensors (or detectors) described herein may be, or have portions thatare, a stand-alone unit that can be connected to an inlet and an outlettube or pipe. The flow detectors described herein may be a system thatis, or have portions that are, fixedly couplable (or attachable) to atube or pipe, such as via a clamp.

In some embodiments, ultrasonic flow sensors may be arranged to measureflow within the airway in the removable unit (or airway). In someembodiments using ultrasonic flow sensors, there are no activecomponents in the removable unit. A mating subsystem of the removableairway may contain tubing, and optionally a means (e.g., a slot, or apin, or other alignment structure) to fixedly couple the matingsubsystem to the ultrasonic source and sensors in the base unit. Thetubing may be metal, plastic, or other suitable material fortransmitting ultrasound.

The ventilator systems described herein may include tubes or tubing. Thetubes or tubing may include a volume contained by surfaces adjacent tothe volume with at least two openings to the volume, such as an inletand an outlet. The geometry of the tubes or tubing is not limited. Forexample, a tube or tubing may have an approximately cylindrical volume,a volume with an approximately square or rectangular cross-section, avolume with a semicircular cross-section, or any other geometry. In somecases, a section of a tube or tubing may be a portion of a sensor. Insome cases, the tubes or tubing may have a section removed, and replacedwith a portion of a sensor. For example a tube or tubing may have a holecut out of one of the sides, or may be formed with a hole in one of thesides, of the tube or tubing and the hole covered with a compliantregion (e.g., forming a portion of a pressure sensor, as describedherein) or a diaphragm (e.g., forming a portion of an acoustic flowsensor, as described herein). The hole covered by the portion of thesensors may also be sealed, such that no air can escape the tube ortubing through the hole of (or adjacent to, or in the vicinity of) thesensor portion. In some cases, the tubes or tubing may have separatesections, where the separate sections may be of different materials ordimensions. For example, a portion of the tubing that is used in thepinch valve (e.g., a portion of the tubing in the vicinity of the pinchvalve) may be a highly compliant material such as silicone, and thetubing upstream and downstream from the pinch valve may be vinyl, whichis less compliant. This may be advantageous in that vinyl tubing may beless expensive than silicone tubing, thus lowering the overall cost ofthe removable unit by using silicone tubing only in the regions wherehigh compliance is required.

In some embodiments, ventilator systems described herein may measureflow with optics, such as by interferometry or by a Schlieren-typeshadowgram (e.g., using Schlieren photography, or shadowgraphs). Suchsystems measure flow that is related to disturbances in the airway suchas turbulence or induced Karman vortices. Such sensors could include anoptical system (e.g., including a light source and a detector, where thedetector is an array of photodetectors, or a camera (e.g., a CCDcamera)), and one or more windows for light to enter and exit an airwaycontaining a flowing gas. Light from the sensor's optical system wouldpass into the airway via a first window (or first window portion)including an optically transmissive material. The light would exit theairway through a second window (or second window portion) afterinteracting with the gas in the airway. The first and second windows maybe the same window or different windows, and the first and second windowportions may be portions of the same window, or portions of differentwindows. The first and second windows (or window portions) may be flatsuch that they do not distort or redirect the incoming light, or may beone or more lenses.

In some embodiments, ventilator systems described herein may measureflow using a mechanical means in the removable airway, such as using apaddle wheel or turbine in the air flow within a tube. Air flow withinthe removable airway would cause the wheel or turbine to rotate. Themovement of the paddle wheel or turbine can be measured by external(i.e., in the base unit) light source and detector means (e.g., anelectric eye, as described herein), whereby the paddle wheel interruptsthe light from the source (e.g., by impinging upon a part of a rotatingwheel or turbine) and changes the intensity detected by the detector asthe rotating part moves. The light may be reflected, refracted,diffracted, or pass through in such a position that it is interruptedand then not interrupted periodically. The flow sensors can becalibrated, such that the rate of the changes in light intensity can beconverted to the speed of the rotating means and the flow rate. In someembodiments, the rotating wheel or turbine may have a means for slowingthe rotation as by braking. The brake may be used to detect lower flowsafter a period of higher flow where the wheel may continue spinning dueto momentum of the wheel at a speed which would indicate a higher flowthan the actual reduced flow, where the brake may be temporarily appliedto reduce the speed of the wheel such that the wheel's speed may soonerrepresent the actual flow rate. The brake may be electrostatic, whereinat least two generally adjacent conductive regions are placed outsidethe airway to which a potential difference is applied, in the manner ofan electrostatic gripper or chuck. The brake may be turned onperiodically and or at regular intervals, such as every tenth of asecond, or every 1 second. This can aid in the detection of reduced flowrates, as the rate at which the wheel slows down may be less than therate at which the flow drops resulting in a measurement with a time lag.The brake may also include an electrorheological or magnetorheologicalfluid contained within a system coupled to the rotating wheel or turbinewithin the airway and acted upon by an electric or magnetic field. Theelectric or magnetic field may be provided by a subsystem in the baseventilator, or by a subsystem within the airway (e.g., where electricalenergy is provided by the base ventilator system via an electricalconnection to the airway).

In some embodiments, the ventilator systems described herein include oneor more flow sensors that can detect the transduction of sound generatedby a flowing medium such as a gas. In some embodiments, the ventilatorsystems described herein include one or more flow sensors that detect aflow (e.g., within a tube) by measuring a sound generated by a flowingmedium such as a gas. In some cases, the sensor may include a portion(e.g., that is part of the removable unit or airway) with an inlet andan outlet. In some cases, the sensor may include components that detectsound, for example, sound generated by gas flowing in a tube, where thecomponents are outside the tube (e.g., where the components are part ofa portion of the sensor contained in a base unit). In some cases, afirst component of the sensor is coupled to (or inside of) the tube(e.g., that is part of the removable unit or airway) and a secondcomponent of the flow sensor is outside (and not connected to, or nottouching, or touching but not connected to) the tube (e.g., that is partof the base unit).

In some embodiments, the ventilator systems described herein include oneor more acoustic flow sensors that measure the flow of a fluid bymeasuring the sound(s) generated from the flowing fluid. In some cases,acoustic flow sensors contain a diaphragm that forms a part of (or iscoupled to) a tube of the removable airway, wherein air (or are withother material) flowing in the tube cause the diaphragm to emit a sound.The acoustic flow sensors may further include a sound sensor (e.g.,microphone) included in a base unit configured to measure the soundgenerated by the diaphragm. In some cases, the tube of the removableairway further includes one or more structures configured to generatesound, as described herein. In some cases, insulating regions surround(or are adjacent to) a portion of the tube that generates sound inresponse to flow within the tube and/or the microphone, to insulate thetube region and/or the microphone from sounds (e.g., noise) generatedoutside of the portion of the tube, as described herein. In some cases,the acoustic flow sensors contain structures and or more than onemicrophone to detect a rate and a direction of flow within a tube. Thesound generating region(s) (e.g., diaphragms and/or structures in thetube) may be in more than one location within the tube, and/or maysurround the tube. The sound generating region(s) may be a section ofthe tube such as a thin section (diaphragm) such that sound is emittedgenerally radially outwards all around the tube. In some cases, achamber may be disposed around the tube to collect sound from manydirections emitted by the tube. In some cases, the tube sectionsadjacent to the sound sensing section may contain sound blockingelements to isolate a sound sensor (e.g., microphone) from environmentalsound, such as by forming a path that snakes back and forth, and maycontain sound-absorbing and dampening surfaces.

In some cases, a first portion of a flow sensor is a tube that is partof the removable unit (airway), and a second portion of a flow sensor isa microphone that is part of the base unit. In such cases, the tube maybe configured to transmit sound in a frequency range of interest (e.g.,in a frequency range where a flowing gas in the tube will generatesound, and where the microphone can detect the sound). For example, thematerial of the tube may be chosen to transmit sound, and/or the tubemay be designed to efficiently generate sound in response to a flowinggas within the tube (e.g., contain structures as described herein).

In some embodiments, the flow rate may be detected by placing anaccelerometer (that is part of the base unit) against the diaphragm(that is part of the removable unit) of an acoustic flow sensor. In suchcases, the support and connection of the accelerometer to the base unitwould favorably have a lower compliance than the diaphragm. In someembodiments, the movement of the diaphragm may be detected by havinglight from the base unit impinge on the diaphragm and subsequently bedetected by a light detector in the base unit, wherein changes in thelight due to movement of the diaphragm may be detected. In some cases,an accelerometer, for example forming a portion of an acoustic flowsensor, may be incorporated into the removable unit.

In some embodiments, a diaphragm may contain a coil of wire, and thebase unit may contain a magnetic-field generating means, such as apermanent magnet. The coil of wire on the diaphragm may have electricalconnections, for example at positions that are fixed on a rigid sectionof the removable unit. The electrical connections may couple toelectronics (e.g., the control system) in the base unit for detecting acurrent in the coil. When the coil moves due to sound generated from theflowing gas within the airway, it will generate a current due to aproximity of the coil to the magnetic field provided by base unit. Thecoil may be similar to coils used in common speakers. In an alternateembodiment, a magnetic field generating means, such as a magnet, may bemounted on the diaphragm, and a magnetic field detecting means, such asa coil or a magnetometer, may be in the base unit. In some embodiments,the magnetic field generating means on the diaphragm may be a coil. Insome cases, the field generating means and the field sensing means(e.g., a coil, magnetometer, Hall sensor, or any device capable ofdetecting a magnetic field) may be coupled via a negative feedbackamplifier system (e.g., in the control system) such that the amplifierdrives field sensing or field generating means coupled to the diaphragm(e.g., a coil) in such a manner that the field sensing or fieldgenerating means coupled to the diaphragm remains in a steady state,such as an approximately fixed position, or vibrating at anapproximately fixed amplitude or frequency. The signal in the negativefeedback amplifier that results in the approximately steady position ofthe diaphragm may be used as a signal representing the amplitude ofsound within the airway.

In some cases, an acoustic flow sensor may also measure other parametersof a flowing gas, such as pressure and/or temperature. In some cases, anacoustic flow sensor may work in conjunction with another one or moresensors that measure other parameters of a flowing gas, such as pressureand/or temperature. A processor (e.g., that is part of the controlsystem) may convert the detected sound (e.g., intensity and/orfrequency) and another detected parameter (e.g., temperature and/orpressure) to a flow rate of the gas. In some cases, a measured flow rateof a gas and another detected parameter (e.g., temperature and/orpressure) can be used by the control system to convert a gas flow rateto an amount of gas (e.g., air, or oxygen) moving past (or through) thesensor (or moving within a tube). In some cases, the total amount of gasmoving through the sensor system may be calculated from inputs fromindependent flow, pressure, and temperature sensors.

In some cases, the gas within the ventilator system is air, where theair may be any suitable gas used in the ventilator systems describedherein, such as a combination of oxygen and air in various proportions,air exhaled from a patient that also contains other material (such asliquid particles, pathogens, and/or medicinal aerosols), or air mixedwith any other contaminants (e.g., from the patient, or a gas sourcecoupled to the system).

In some cases, the flow detectors (sensors) described herein may have ameans to calibrate the detected sound to a flow rate, for example, wheresuch flow rate is measured by a preconfigured and calibrated detectorsystem. The flow sensors described herein may have adjustments or inputsof calibration data or settings. The airway may have calibration datastored in a machine-readable format printed on its surface, such aslinear or 2D barcode.

In some embodiments, the ventilator system described herein containpressure sensors that have components in removable unit (airway) and inthe base unit. In some cases, pressure may be measured by deformation ofa surface (e.g., a compliant region) of the removable airway. Thedeformation may occur in a region that has a lower compliance than thesurrounding region enclosing the airway such that when the pressure inthe airway increases, the softer region pushes outwards. The deformationof the compliant region may be detected using one or more sensorportions (e.g., force sensors, load cells, or electric eyes) containedin the base unit, as described herein. In some embodiments, the pressuresensor may include a driven oscillator and changes to the oscillationmay be converted into a pressure. Such a system may be composed of acoil mounted on a diaphragm and a permanent magnet mounted on the base,where the coil is driven at a fixed amplitude and frequency. Changes inamplitude, phase, or frequency may be translated into pressure changes.

In some cases, the airway may also contain a humidity sensor.

In some cases, a calibrating system may be attached to the inspiratoryand expiratory ports of the removable airway while it is in place in thebase ventilator unit of the ventilator. The calibrating system may haveactive sensors, such as flow, pressure, and temperature sensors, and maycontain an electrical port to connect to the base ventilator system. Thebase unit may have a setting or be configurable to flow gas at a setrate or at a range of rates that may be detected by the calibratingsystem. In this manner, the calibration of the airway may be checked andadjusted either with manual inputs or automatically via an electricalconnection from the base unit to the calibrating system. The calibratingsystem may also include a fixed tube, such that at a predeterminedsetting of the valves a known amount of gas is expected to flow in thefixed tube, and a measured flow may be compared to the expected flow tocalibrate the ventilator system. A fixed tube may be a tube that has arigid and fixed geometry, for example a tube that is molded in rigidplastic and is provided as a component of the ventilator system. Theventilator base unit may have preprogrammed settings and/or sequences ofsettings and readings considered as a calibration routine that may bebuilt into the ventilator system (e.g., into the control system).

Example Systems

FIG. 1 is a simplified schematic of an example of an inhale manifold1000 of a ventilator system, in accordance with some embodiments. Theinhale manifold 1000 contains tubes 1, 4, 6, 10, 14 and 27, connectors 3and 13, bellows 7, weight 8, valves 5 and 9, pressure-limiting andpressure-detection subsystem 11, flow sensor subsystem 12, and pressuresensor subsystem 31. Tube 1 contains gas to deliver to the patient(e.g., a mixed gas with a particular FiO₂, pure air, or pure oxygen).Inhale manifold 1000 may contain a device or subsystem (not shown) forthe generation of a mixed gas with a particular FiO₂ from pure oxygen.The tube 1 connects to a connector 3 to a tube 4, with a direction ofgas flow 2. Tube 4 connects to valve 5, which connects to tubes 6. Tubes6 connects to bellows 7, and valve 9. The outlet of valve 9 connects viatube 10 to a pressure-limiting and pressure-detection subsystem 11 andflow sensor subsystem 12. The outlet of flow sensor subsystem 12connects via tube 27 to a connector 13 which connects to tube 14 whichleads to the patient inhale tube, such as the inlet of patient circuit,where gas flows in direction 15.

FIG. 2 is a simplified schematic of an example of an exhale manifold2000 of a ventilator system, in accordance with some embodiments. Theexhale manifold 2000 contains tubes 17, 19 a, 19 b, and 24, connector29, bellows 21, weight 22, valves 18 and 23, pressure-maintainingsubsystem 20, flow sensor subsystem 30, and exit port (e.g., including afilter) 25. Tube 28 leads from a patient's lungs such as via a patientcircuit and/an endotracheal tube to a connector 29 which connects totube 17, with gas flow direction 16. The inlet tube 17 connects to valve18. The outlet of valve 18 connects to the tube 19 a. Tube 19 a connectsto the pressure-maintaining subsystem 20. Gas passing through thepressure-maintaining subsystem 20 enters tube 19 b and a bellows 21.Tube 19 b connects also to valve 23, whose outlet tube 24 connects toexit port 25 which expels gas 26 to atmosphere. The output of valve 18may also pass through a flow sensor 30.

There are several modes of operation of a ventilator system includinginhale manifold 1000 and exhale manifold 2000. A control system (notshown) may monitor signals from pressure-limiting and pressure-detectionsubsystem 11, flow sensor subsystem 12, pressure sensor subsystem 31,pressure-maintaining subsystem 20, and flow sensor subsystem 30, andthen adjust (e.g., based on the signals) valves 5, 9, 17 and 23, andother components of the system (e.g., bellows 7 and/or 21). The controlsystem adjusts the valves in the ventilator system according todifferent modes of operation.

In a tidal volume inhalation control mode, valve 5 is opened and valve 9is closed. The bellows 7 which will be described below inflates (e.g.,due to air pressure) to a pre-determined volume, such as 500 cc, from 50cc to 1000 cc, or from less than 50 cc to more than 1000 cc. When thepredetermined volume has been reached, the control system closes valve 5and opens valve 9. Valves 18 and 23 may be open or closed duringinflation of the bellows 7. When valve 9 opens (e.g., and valve 18and/or 23 is closed), gas begins to inflate the lung of the patient (notshown), and pressure builds in the pressure-limiting andpressure-detection subsystem 11. For example, valve 18 may be closedwhen valve 9 opens such that bellows 22 is isolated from the patientwhile gas from the inhale manifold 1000 inflates the lung of a patient.In cases where there is no bellows 22 on the exhale manifold 2000, thenvalve 23 may be closed and valve 18 may be open, or both valves 18 and22 may be closed. When pressure in pressure-limiting andpressure-detection subsystem 11 reaches a predetermined value, or PIP(e.g., about 30 cmH₂O, about 40 cmH₂O, or from 15 cmH₂O to 45 cmH₂O, orfrom less than 15 cmH₂O to more than 45 cmH₂O), valve 9 is closed by thecontrol system, completing the inhale cycle. Valve 5 may then be openedto fill the bellows 7 to be ready for the next inhale cycle of thismode.

When valve 9 closes, the exhale cycle of this mode may commence. Thecontrol system may have a predetermined user-settable or fixed delay,such as 1 second or less to 3 seconds or more, such that valve 18 mayopen after the delay has passed. The delay may be zero in some cases.When valve 18 opens, gas begins to pass from the lungs into the tube 19a. In one mode, valve 23 may be closed during a first portion of theexhale cycle. Subsystem 20 maintains the pressure at or above a presetvalue (e.g., about 5 cmH₂O, or from 2 cmH₂O to 15 cmH₂O, or from lessthan 2 cmH₂O to more than 15 cmH₂O), and the bellows 21 fills withexhaled gas. Gas may also flow through a flow sensor subsystem 30. Theend of the first portion of the exhale cycle may be determined either bythe bellows 21 reaching a predetermined volume, or by the flow sensor 30detecting a pre-determined low level of flow, such as no flow, or by thepressure sensor reaching a preset minimum value (PEEP). When any ofthese end-of-exhale conditions is reached, the control system closesvalve 18 and open valve 23, initiating a second portion of the exhalecycle. In the second portion of the exhale cycle, gas in the bellows 21is emitted through filter 25 to the atmosphere, thereby completing theexhale cycle. After the exhale cycle is complete, there may include adelay (e.g. , of 1 second or less and up to 3 seconds or more) beforerepeating the inhale cycle, as described above.

In another mode of operation, a pressure control mode, the ventilatorsystem uses the PIP, as determined by a preset value of the peekpressure-limiting and pressure-detection subsystem 11, to control thesystem. In this mode, both valves 5 and 9 are opened simultaneously(e.g., and valves 18 and/or 23 are closed) at the start of an inhalecycle. The lungs of the patient inflate to a pressure that stopsincreasing due to the action of the pressure-limiting andpressure-detection subsystem 11. When the limiting pressure is reached,the control system receives a signal from pressure-limiting andpressure-detection subsystem 11 (e.g., indicating that a PIP has reacheda threshold value, e.g., about 30 cmH₂O, about 40 cmH₂O, or from 15cmH₂O to 45 cmH₂O, or from less than 15 cmH₂O to more than 45 cmH₂O),and the control system closes valve 9. The exhale cycle is theninitiated as described above with respect to the tidal volume inhalationcontrol mode (e.g., with suitable delays). As above, the end of theexhale cycle may be determined via flow sensor 30 or a volume of bellows21. After the exhale cycle is complete, there may include a delay (e.g.,of 1 second or less and up to 3 seconds or more) before repeating theinhale cycle described above.

The preceding two modes of operation are commonly referred to as“Mandatory Breathing” mode. Another clinically desirable mode iscommonly referred to as “Triggered” or “Spontaneous” breathing mode. Ina triggered breathing mode, at the end of an exhale cycle, with valve 9closed and valve 5 open, pressure sensor subsystem 31 may be monitoredfor a negative pressure (e.g., about negative 2 cmH₂O, or from negative4 cmH₂O to negative 2 cmH₂O, or from less than negative 4 cmH₂O to morethan negative 2 cmH₂O), and a negative pressure threshold may be set toa predetermined value. When the negative pressure threshold in pressuresensor subsystem 31 is reached or the pressure is pressure sensorsubsystem 31 more negative than the threshold, then the control systemmay open valve 9. The pressure-limiting and pressure-detection subsystem11 may be set to a predetermined value (e.g., about 10 cmH₂O, or from 4cmH₂O to 20 cmH₂O, or from less than 4 cmH₂O to more than 20 cmH₂O),such that the breathing is assisted by a background pressure aboveatmospheric pressure. The end of the inhale cycle in this triggeredbreathing mode may be determined by the flow sensor subsystem 12detecting a preset low level of flow (e.g., about 3 liters per minute(lpm), from 0.1 lpm to 10 lpm, or from 1 lpm to 10 lpm, or from 0.1 to 1lpm). In this mode, the exhale cycle may be the same as described abovefor the mandatory breathing modes, and the exhale cycle end may bedetermined by volume exhaled or by flow rate. Additionally, after theexhale cycle is complete, there may include a delay (e.g., of 1 secondor less and up to 3 seconds or more) before repeating the inhale cyclefor the triggered breathing mode (as described above).

The valves 5, 9, 18 and/or 23, in inhale manifold 1000 and exhalemanifold 2000 may be pinch valves, in some embodiments. Valves 5, 9, 17and/or 23 may be configured to variably adjust the flow of gas throughthe valve (i.e., through a tube passing through the valve, or through acompressible section of a tube passing through the valve), as describedherein.

FIGS. 3A and 3B are simplified schematics of an example of a pinchvalve, in accordance with some embodiments. FIG. 3A shows the valve inan open state (or position), and FIG. 3B shows the valve in a closedstate (or position). The valve in this example contains valve body 32, amoveable element 34, and a fixed element 33. In FIG. 3A gas-containingtube 31 passes through the open valve where tube region 35 is in an openstate. When an actuator (not shown) within the valve body 32 isactuated, element 34 is pushed into tube 39, closing the valve. FIG. 3Bshows the valve in a closed state, where the moveable element 34compresses the tube 39 against fixed element 33 in a tube region 38.Tube region 38 is a compressible section of the tube 39. In some cases,when the valve is closed the tube is closed and no gas (or a limitedamount of gas) can pass at pressures reached in the ventilator system.The valve body 32 is fixed spatially with respect to the tube backstop33. When the valve in this example is open, such as when the moveableelement 34 is in the position shown in FIG. 3A, the tube 31 can beremoved from the valve. The valve shown in FIGS. 3A and 3B may beconfigured to variably adjust the flow of gas through the valve (i.e.,through a tube passing through the valve, or through a compressiblesection of a tube passing through the valve), as described herein. Forexample, moveable element 34 may have a plurality of positionsconfigured to compress the tube 31 by varying amounts.

FIGS. 4A and 4B are simplified schematics of another example of a pinchvalve, in accordance with some embodiments. FIG. 4A shows the valve inan open state (or position), and FIG. 4B shows the valve in a closedstate (or position). The valve in this example contains valve body 46, aroller 44, an arm 48, an axle 52, and a fixed element 43. In thisexample, a roller 44 may compress the tube 41 by rotating around axle 52on arm 45. The rotation of arm 45 is actuated via a rotary actuator invalve body 46. FIG. 4A shows the arm 48 and the roller 44 at openpositions and tube region 42 of tube 41 is open, such that gas may passthrough region 42. FIG. 4B shows the arm 48 and the roller 44 in aclosed position, where the roller 44 is pushed into tube 47 and tuberegion 49 is compressed against fixed element 43 such that no gas (or alimited amount of gas) can pass at pressures reached in the ventilatorsystem. Tube region 49 is a compressible section of the tube 47. Thevalve body 46 is fixed spatially with respect to the tube backstop 43.When the valve in this example is open, such as when the arm 48 androller 44 are in the positions shown in FIG. 4A, the tube 41 can beremoved from the valve. The valve shown in FIGS. 4A and 4B may beconfigured to variably adjust the flow of gas through the valve (i.e.,through a tube passing through the valve), as described herein. Forexample, arm 48 may have a plurality of positions configured to compressthe tube 41 by varying amounts.

In some cases, the rotary actuator is a motor, such as a gearhead motor.An advantage of the valve shown in FIGS. 4A and 4B is that a wide rangeof motor specifications will meet the need of the valve. In some cases,a rotation rate of the output shaft in RPM has a minimum value of 30 RPMor less, and a torque minimally sufficient to be able to compress thetube.

FIG. 5 is a simplified schematic of the pinch valve shown in FIGS. 4Aand 4B, in accordance with some embodiments. The time to close the valvein this example may be minimized by having an open position where theroller 44 is close to the tube 41, with a small distance 58 between theroller 44 and the tube 41, as shown in FIG. 5. In this example, theangle 55 between the arm 48 and a line 57 (where line 57 isapproximately perpendicular to the tube) is a fraction of 360 degrees,such as 30 degrees, and the distance in the open position between theroller and the tube is small, such as 0 mm or 1 mm, or 2 mm, or from 0mm to 3 mm, or from less than 1 mm to more than 3 mm. If the rotationrate of the arm 48 is 30 RPM, and the angle 55 is 30 degrees, then thetime to close the valve is approximately 0.3 seconds. A lower RPM mayalso be used if a longer closing time is acceptable. A higher RPM may beused if a shorter closing time is required. In some cases, the openposition of the valve shown in FIG. 5 allows insertion and removal ofthe tube. In some cases, the valve has an open position used duringoperation, and a tube removal position where the roller 44 is moved awayfrom tube 41 when the tube 41 is removed from the valve.

In some cases, pinch valves with rotary elements for the ventilatorsystems described herein can use motors with 30 RPM and a torque of 40gram-cm. For example, such a motor can be used to compress a siliconetube (e.g., with a ½″ diameter).

The tubes in the ventilator systems described herein, e.g., those shownin FIGS. 1-5, may be of any flexible material such as vinyl or silicone.The motor used by the valves in the ventilator systems described herein,e.g., those shown in FIGS. 1-5, may be a DC motor. A control circuit mayposition the motor by turning it on and off. In some cases, the positionof the motor may be determined by an electric eye, where the electriceye includes a light emitter and a light sensor.

FIGS. 6A and 6B are simplified schematics, in front view and side view,respectively, of an example of a system for controlling the position ofa valve, in accordance with some embodiments. The system shown in FIG.6A includes a generally non-light-transmissive (or opaque) disc 65mounted on a rotary actuator shaft 66. The arm 59 may be the same as arm48 in FIGS. 4A, 4B and 5. The disk 65 has two slots 63 and 64 cut intoit, and an angular separation 62 generally the same as the angle 61between the arm 59 and a direction 60 similar to direction 57 in FIG. 5(i.e., that is approximately perpendicular to the tube (not shown)). Thetwo slots 63 and 64 may be positioned anywhere on the disc 65 as long asthe angle between them is generally angle 62. A single electric eye maybe disposed fixedly with respect to the disc 65 to detect two positions.FIG. 6B shows the disc 65 from a side view. Slot 63 is shown disposedbetween a light source 69 and a light detector 70 comprising theelectric eye. When at the position shown in FIG. 6B, the detector willdetect light. At other positions, it will detect less light. Thisdifference can be used to determine by the control system when the valveis in different positions. The slots 63 and 64 can be located tocorrespond to certain positions of the valve, e.g., an open position anda closed position. In some cases, there can be more or fewer than twoslots to indicate more than two valve positions, e.g., an open position,a closed position, and a position for removing the tube from the valve.Valves using the systems shown in FIGS. 6A and 6B may be configured tovariably adjust the flow of gas through the valve (i.e., through a tubepassing through the valve, or through a compressible section of a tubepassing through the valve), as described herein. For example, there maybe a plurality of slots (not shown) that correspond to a plurality ofpositions configured to compress a tube passing through the valve byvarying amounts.

In operation, the rotary actuator may be turned on until light isdetected through slot 63 at which point the actuator may be turned off.For example, when light is detected through slot 63, the valve is in theopen position. When the valve is to be closed, the control system mayturn on the rotary actuator, until light is detected through slot 64 andthen the control system may turn off the actuator, leaving the valve inthe closed position. The angle 62 between the slots may be more or lessthan the angle 61 where the control system may have predetermined delaysbetween detecting the slot and turning off the rotary actuator. Suchdelays may be useful in achieving a precise closed or open position ifthe rotation takes some time to stop after being initiated. In somecases, the slots (e.g., 63 and 64) may be at positions in advance of thefinal desired resting position. The closed positions may also becontrolled such that the valve does not press on the tube with too muchforce (e.g., which could damage the tube, or reduce the lifetime of thetube). In the case of a pinch valve with a rotating movable element, themaximum compression of the tube may be set by the geometry of themovable element (and a roller coupled thereto), or by setting limits onthe position of the movable element. In the case of a pinch valve with alinear movable element, the maximum compression of the tube may be setby setting limits on the position of the movable element.

In another embodiment (not shown), instead of slots, the disc may have acontrasting region, such as darker regions, with the emitter anddetector on the same side of the disc configured to illuminate anddetect the contrasting regions.

FIG. 7 is a simplified schematic of an example of a system forcontrolling the position of a valve, in accordance with someembodiments. In this example, the disc of the system in FIGS. 6A and 6Bmay be replaced with element 72 (in the example shown in FIG. 7, element72 is a section of an annulus) with a leading edge 73 and a trailingedge 74 such that an electric eye 75 may detect a light transmissionchange when the edges 73 and 74 pass through the electric eye. Electriceye 75 may include a light source and detector (not shown) configuredsimilar to that shown in FIG. 6B, or configured on the same side aselement 72 as described above. Element 72 may be of any shape that has aleading and a trailing edge and is of a material that is generallynon-light-transmissive for light at the wavelength of the emitter in theelectric eye.

In some embodiments, a disc or other element having a generallylight-transmissive material at the wavelength of the light detected bythe electric eye can be used in the valve control systems describedherein. In such cases, regions that are non-light-transmissive aredisposed on the perimeter of the disc or other element in a mannersimilar to slots 63 and 64, which are detectable as a change (reducedlight detection) by the electric eye they pass through it.

In other cases, a different means of detecting two positions (or aplurality of positions) of the rotation of a valve (e.g., the valvesshown in FIGS. 1-5) are envisioned, such as limit switches, proximitysensors, rotary encoders, and the like. The rotary actuator of a valve(e.g., the valves shown in FIGS. 1-5) may be a DC motor, a steppermotor, a servo motor, or a pneumatic motor.

FIG. 8 is a simplified schematic showing an example of pressure-limitingand pressure-detection subsystem 11 (of FIG. 1), in accordance with someembodiments. The pressure-limiting and pressure-detection subsystem 11includes a container 76 that can hold a fluid 77 such as water or oil,and a tube 78. Tube 78 (e.g., a rigid tube, or a tube configured suchthat the height 79 is controlled) is disposed such that its distal end87 is below the surface 88 of the liquid. In operation, if a pressureinside the tube 78 is below a pressure determined by the height 79 of acolumn of liquid, no gas will be released, and the surface 80 of theliquid inside the tube will be at a position between the surface 88 ofthe liquid and the tip 87 of the tube. When the pressure inside the tubeis at or greater than that of the column of liquid of height 79, gaswill escape into the liquid. Pressure above the height of the column ofliquid will be released as increased flow and the pressure inside thetube will generally not exceed that of the height 79 of the column ofliquid. For example, in some embodiments, the height 79 is 30 cm and theliquid is water, so the limiting pressure inside of tube 78 (and hencein a portion of the airway of the ventilator system) is 30 cmH₂O. Thislimiting pressure is commonly referred to as PIP (Peak InspiratoryPressure). The limiting pressure may be adjusted by moving the tip ofthe tube 87 closer to or farther from the surface 88 of the liquid.

In some cases, pressure-maintaining subsystem 20 (of FIG. 2) in theexhale manifold may be of the same or similar configuration as describedabove for pressure-limiting and pressure-detection subsystem 11. Inoperation, when the inhale is switched over to the exhale cycle, gas inthe lungs of the patient may be at a higher pressure than a desiredminimum maintained pressure, such that gas nearly immediately begins tobubble out of the water. As the system is closed to atmosphere orincoming gas, it is sealed with the lungs of the patient, so gas may bereleased through the subsystem 20 until the minimum preset maintainpressure is reached. This pressure is commonly referred to as PEEP. Theliquid container for the PEEP control is sealed, such that all gas thatbubbles through enters tube 19 b in FIG. 2.

FIG. 9 is a simplified schematic showing an example of a pressure limitdetection subsystem 9000, in accordance with some embodiments. The endof the inhale cycle, or the reaching of the pressure limit, may bedetected using subsystem 9000. In some cases, subsystem 9000 may be usedas pressure-limiting and pressure-detection subsystem 11 in FIG. 1,and/or pressure-maintaining subsystem 20 in FIG. 2. When the pressure inthe tube 85 meets or exceeds the limiting pressure set by the depth ofthe tip 89 of the tube below the liquid surface, bubbles will come outof the tube. The tip 89 may be cut at an angle to force the bubbles togo in a particular direction. The tip of the tube may also be benttowards a direction of desired bubble travel. Disposed outside of theliquid-containing vessel 90 is an electric eye composed of a lightsource 83 and a detector 84. When bubbles 91 are emitted from the tube85, they rise and intercept the light path 92 in the electric eye, suchthat the electric eye detects less light when a bubble passes. In thisway, a control system (e.g., controlling valves, and other components ofthe ventilator systems described herein) can detect the reaching of thepressure limit.

In other embodiments, the electric eye in subsystem 9000 may beconfigured with the emitter and detector both facing generally the sameway in proximity to each other where the light from the emitter reflectsoff of a reflective surface, such as a retroreflective surface, or ahigh contrast light and dark surface. When bubbles intercept the path ofthe light (before and/or after reflecting off of the reflective surface)the electric eye will detects less light, and can provide a signal tocontrol system as described above.

FIG. 10 is a simplified schematic of an example of a bellows 7 (of FIG.1), in accordance with some embodiments. The inhale cycle may becontrolled by a subsystem that can have a preset fill volume, determinedby bellows 7. An expandable container 93 is connected to a tube 95. Whengas enters through tube 95, the container expands, with upper solidsurface 94 moving in a direction 97. The upper surface has disposed onit an opaque member 96 that can rise until it interrupts the electriceye with source 98 and detector 99. The position of the electric eyedetermines the volume reached when the electric eye is triggered. Insome cases, when the predetermined volume is reached, valve 9 is opened(e.g., by a control system that has received a signal from the electriceye that a fill volume has been reached) and the gas is transferred fromthe ventilator system to the lungs of the patient. A weight 100 can bedisposed to compress the expandable container 93 and eject air into thelungs. In some cases, bellows 21 of FIG. 2 in the exhale manifold may beof the same or similar configuration as described above for bellows 7 ofFIG. 10.

FIG. 11 is a simplified schematic of another example of bellows 7 (ofFIG. 1), in accordance with some embodiments. In some embodiments, theexpandable gas container of the bellows 7 is a bag of non-rigid (orflexible) material 103, such would be achieved by a silicone membrane ofthickness less than 0.5 mm, as shown in FIG. 11. In this example, gasenters through an inlet 104 to a bag of non-rigid (or flexible) material103, which when filled lifts a piston 102 held in position via acylinder 101. The volume of gas inside bag of non-rigid (or flexible)material 103 increases as it is filled such that the piston moves up indirect proportion to the gas volume increase in the bag. In some cases,bellows 21 of FIG. 2 in the exhale manifold may be of the same orsimilar configuration as described above for bellows 7 of FIG. 11.

FIG. 12 is a simplified schematic of another example of bellows 7 (ofFIG. 1), in accordance with some embodiments. In this example, gasenters via a nozzle 105, inflating soft bag 106, which lifts a plate 108hinged at 109 with respect to a fixed plane 107. In some cases, theposition of plate 108 is calibrated with respect to the volume of gasinside of bag 106.

In some embodiments, bellows 7 in FIG. 1 and/or 21 in FIG. 2, eachcontain a generally inflatable container that expands to push an opaquemeans (e.g., a plate, a block, or an opaque, or reflective object) tointerrupt an electric eye. The opaque means may or may not be directlyconnected to the inflatable container. In some cases, the opaque meansmay be attached to a repeatably movable means (e.g., a moving rod,wheel, or piston) that is part of the base unit.

FIGS. 13A-13C are simplified schematics of an example of pressuredetection system 31 (in FIG. 1), in accordance with some embodiments.Pressure detection system 31 in this example includes a liquid 111 in au-shaped tube 110 disposed such that direction 123 is up away from theearth, as is common in u-tube manometers. A pressure is measureddirectly proportional to the difference in height of the two liquidsurfaces 111 and 113, where in FIG. 13A they are at the same height sothere is no pressure difference on either side of the liquid 111 in tube110. In FIG. 13B, the pressure is greater on side 125 of the tube andlevel 116 is below level 117. The pressure difference may be read onscale 122. In FIG. 13C, the pressure difference is negative, with height119 detected at a preset level by the position of an electric eyeincluding emitter 120 and detector 121. Such a negative pressuredetection may be used to initiate triggered breathing. Additionally, insome cases the peak plateau pressure in the lungs (i.e., the pressurereached after inspiration is halted and pressure in the lungsequilibrates) may be measured with the manometer using the scale 122.

FIG. 14 is a simplified schematic of an example of flow sensor subsystem12 and 30 in FIGS. 1 and 2, in accordance with some embodiments. Theflow sensor in FIG. 14 includes inlet 127 into a container 128 that isgenerally tapered outwards from inlet 127 towards outlet 132, where upaway from the earth is direction 133. A ball 129 is free to move insidethe container 128. When gas enters, the ball moves upwards, out of thepath of an electric eye of emitter 130 and detector 131, thus enablingthe control system to detect flow. The minimum flow may be adjusted byvertically adjusting the position of the photodetector.

In some embodiments, the end of the exhale cycle may be detected by alack of bubbles in the PEEP-setting water container system (e.g.,pressure-maintaining subsystem 20 in FIG. 2), for example, using anelectric eye as described above.

FIG. 15 is a simplified schematic of an example of a complete gasmanifold (e.g., airway) of a ventilator system, without valves, inaccordance with some embodiments. Gas (e.g., air, or oxygen mixed withair) enters at 141 into tubing 146. The manifold may be a rigid fixedunit, where all subsystems and components are fixed in place withrespect to each other, for example mounted on a rigid plastic plane. Themanifold as a unit can be placed into the base ventilator unitcontaining the valves, control unit, electric eyes, and an adjustmentinterface and mechanics. Sections of tubing 134, 135, 136, and 137 areinserted into the pinch valves (e.g., as shown in FIGS. 3A-7). Theexpandable containers are 138 and 139 (e.g., as shown in FIGS. 10-12). Afirst portion of flow sensor 140 and a first portion of flow sensor 150are included in the manifold, and a second portion of each of the flowsensors (e.g., the electric eyes) are located in the base ventilatorunit (e.g., as shown in FIG. 14). A portion of a pressure sensorincludes manometer 144 (e.g., as shown in FIGS. 13A-13C). The PIP is setby maximum-pressure unit 147 (e.g., as shown in FIGS. 8-9), with excessgas exited through filter 148 to atmosphere. The gas exits to thepatient at 142. Gas exhaled from the patient enters at 143. Theminimum-pressure maintaining subsystem 149 (PEEP) (e.g., as shown inFIG. 8) is in series with the flow sensor 150 (e.g., as shown in FIG.14) which exits to bellows 139 (e.g., as shown in FIGS. 10-12) which canmeasure the exhaled tidal volume. Exhaled gas may then exit throughfilter 151 to atmosphere.

FIG. 16 is a simplified schematic of an example of the complete gasmanifold in FIG. 15, including portions of the sensors in the manifold(e.g., airway) and the electric eye portions of the sensors located inthe ventilator base unit, in accordance with some embodiments. Theportions of the sensors located in the ventilator base unit are electriceyes 153, 154, 155, 156, 157, 158, 159, 160, and 161, and each include alight source and a light detector that may be mounted on the baseventilator unit. Electric eyes 153, 154, 161, and 162 are for valvepositioning of a rotary actuator. Electric eyes 152 and 160 are fordetecting a volume in the bellows. Electric eyes 155 and 159 areportions of the flow sensors in conjunction with the portion of flowsensor 140 and 150 (e.g., containing the container and ball shown inFIG. 14). Sensors 157 and 158 are portions of flow sensors (inconjunction with the container, liquid and tube of the maximum-pressureunit 147, and the minimum-pressure maintaining subsystem 149) thatdetect flow into the pressure relief traps. Electric eye 156 detectsnegative pressure for triggered breathing mode in conjunction with themanometer 144. The valves of the systems shown in FIGS. 15 and 16 may beconfigured to variably adjust the flow of gas through the valves (i.e.,through a tube passing through each of the valves, or through acompressible section of a tube passing through the valve), as describedherein.

In some embodiments, all measurements from the sensors in the ventilatorunit are converted into an interrupt of an electric eye. This cansimplify development and integration, as well as supply chain managementand assembly, and may also reduce the cost of the system. In some cases,the sensors in the ventilator systems described herein use an “electriceye.”

FIGS. 17A-17B are simplified schematics of examples of electric eyes, inaccordance with some embodiments.

The electric eye in FIG. 17A includes light source 163 emitting light166 (generally along line 165) towards detector 164 at distance 167apart such that a non-light-transmissive means 170 can interrupt thelight by inserting it in the path of the light 166 (by moving thenon-light-transmissive means 170 in direction 171).

Alternately, FIG. 17B shows an example where the light emitter anddetector 168 and 160 are next to each other facing in the same directiontowards a fixed surface 175 that reflects incoming light 172 along apath 174 to become outgoing light 173, where the fixed reflectivesurface is a distance 178 away from the emitter and/or detector. Thefixed surface 175 may have a high reflectance and/or low absorption,and/or high specular reflectance, such as reflecting more than 30%, ormore than 50%, or more than 80%, or from 10% to 100%, of the light 172along path 174. A non-light-transmissive object 176 may interrupt thelight path by being inserted in in the path 174 of the light (by movingthe non-light-transmissive object 176 in direction 177), for example, byabsorbing light 172 (or scattering light 172 away from the detector 169,or deflecting light 172 away from detector 169). In other cases, thefixed surface 175 has a low reflectance (and/or high absorption, and/orlow specular reflectance) compared to the object 176 which may have ahigh reflectance, and when the object 176 moves in the path of thelight, it reflects the light from emitter 168 to detector 169, and theintensity of light 173 detected by the detector 169 increases.

All ventilator parameters of the systems shown in FIGS. 15 and 16 areadjustable either electrically or mechanically. Delays between cycleswhich are related to the inhale:exhale time ratio, may adjusted by aninput to a control system such as with a knob and a variable resistor.PIP may be adjusted, for example, by moving the maximum-pressure unit147 (e.g., moving vessel 76 containing liquid 77) up and down, asdescribed above. The PEEP may be adjusted similarly, for example, byadjusting the minimum-pressure maintaining subsystem 149 up and down, asdescribed above. The tidal volumes on inhale and exhale may be adjustedby moving the electric eye sensor up and down, as described above. Theminimum flow in sensors 140 and 150 maybe adjusted by moving theelectric eye up and down, as described above. The triggered breathingpressure may be adjusted by a moving an electric eye sensor up and down,as described above. In some cases, all of these mechanical adjustmentsmay include mechanisms that attach the part to be moved to a slider on apanel that can be adjusted by user. For example, the panel may have 7user-adjustable sliders, one for each of the adjustments describedabove. In some cases, the panel also has two knobs to adjust delaysrelating to breathing rate.

The gas manifold of FIG. 15 may or may not be disposed of betweenpatients. The manifold may be made of low cost plastic materials so thatit is not costly to dispose of between patients. Liquid such as oil orwater is used by the PIP and PEEP pressure traps and the manometer. Insome cases, liquid containing vessels may have a removable lower sectionto allow filling or may have a fitting such as a luer fitting to allowfilling.

In some cases, the electronics of the control system for the ventilatorsystems shown in FIGS. 15 and 16 has no microprocessor. In some cases,all functions may be hard-wired into an analog and/or digital circuit,such that the system has no software. This can be beneficial for safetytesting and development cost.

In some cases, an operator uses the ventilator systems shown in FIGS. 15and 16 by opening a door, inserting the manifold, and filling it withwater in the correct places. The door may be located at the back of theunit opposite the control panel, where the control panel is coupled tothe movable sensors. The operator may then close the door, and mayattach the unit to a patient and a gas source. The ventilator may alsoinclude a means for generating a mixed gas (e.g., containing oxygen,nitrogen, and/or air) and adjusting FiO₂, such that the input gas may bepure O₂ mixed with another gas (e.g., air, or nitrogen). The PIP andPEEP vessels may connect to the rest of the system such as via snappingthem into one or more holders that are connected to a slider foradjustment up and down on the control panel.

In some cases, the ventilator systems shown in FIGS. 15 and 16 mayinclude a screen-type user interface (e.g., an LCD display). In somecases, the ventilator system may include an LED-based user interface(e.g., with a set of LED indicators, or a set of LEDs forming adisplay). In some embodiments, the interface displays the sequencing ofthe valves, and flow, and other sensor data from the electric eyes.Patient data may also be stored and output by the control system.

FIG. 18 is a simplified schematic of an example of a ventilator system,in accordance with some embodiments. A patient 187 is coupled by anair-conducting means (e.g., via a patient circuit 188) to a removablesystem (or removable unit) 186 via a connection 190. The removablesystem (or removable unit) 186 is inserted into the base unit 191, wherethe base unit contains some components of the ventilator system, such asvalves and control system electronics. The contiguous path from thepatient to the removable system is indicated by 189. In someembodiments, the air (or matter contained therein) that is exhaled fromthe patient 187 is contained within removable system (or removable unit)186, such that at no point can the path 189 contact the base unit 191.That is, when the patient is coupled to the removable system (orremovable unit) 186, there is no way for any air or matter to get fromthe patient to a surface of the base unit 191. In some cases, air ormatter from a patient is confined within the removable system (orremovable unit) 186, except for through one or more outlets (e.g.,excess gas exit ports) to the atmosphere. In some cases, the air ormatter from the patient passes through one or more filters beforeleaving an exit port to the atmosphere. In some cases, the exit portsare dedicated exit ports, wherein the exit port is used to expel excessgas to the atmosphere and is not used for any other function (e.g., as asensor port). In some cases, air (or air with additional gases and/ormatter) within the removable airway does not contact any portion of thebase unit without first exiting the removable airway through a(filtered) exit port (e.g., a dedicated exit port, as described herein).Additionally, in some cases, all of the valve components are containedin the base unit, and no valve components can contact the air (or mattercontained therein) that is exhaled from the patient 187.

In some cases, the air from the patient may contact the removable system(or removable unit) 186, and air from the patient may contact a portionof the base unit 191, as long as any contamination on the portion of thebase unit 191 cannot be introduced back into the removable system (orremovable unit) 186 (or a second removable unit that replaces removablesystem (or removable unit) 186 after removable system (or removableunit) 186 is removed from the base unit 191). In other words, anypossible contamination on the base unit 191 cannot cross-contaminate aremovable unit.

In some cases, a patient is a person or animal coupled to the ventilatorvia breathing tubes.

FIG. 19 is a simplified schematic of an example of a ventilator system19000, in accordance with some embodiments. Ventilator system 19000includes a removable system (or removable airway) 179 and a base unit180. The removable system (or removable airway) 179 may be referred toas an airway, or a removable airway throughout this disclosure.Removable system (or removable airway) 179 may have 2, or 3, or 4, ormore than 4 openings (or ports). In some cases, all of the openings tothe removable system (or removable airway) 179 are used to either insertair into removable system (or removable airway) 179, or remove air fromremovable system (or removable airway) 179, and none of the openings tothe removable system (or removable airway) 179 are used for any otherpurpose (e.g., as a sensor port). The removable system (or removableairway) 179 in this example has four ports that are used to insert orremove air from the removable system (or removable airway) 179, and arenot used as sensor ports. For example, opening or port 181 can be usedfor an air supply, opening or port 182 can be used for an air exhaust,opening 183 can be coupled to a patient for inhalation, and opening 184can be coupled to the patient for exhalation.

In another example, removable system (or removable airway) 179 only hastwo ports 181 and 183. In this example, opening or port 181 can be usedfor an air supply and an air exhaust. This may require external valvingof the air supply to alternately connect to the air supply and an airexhaust (which could be atmosphere or a contained system). A connectionto the patient can then be made through a single port 183 for inhalationand exhalation. This embodiment may require internal valving to directsupplied air to the port during inhale and to direct exhausted air tothe exhaust during exhale.

The removable system (or removable airway) 179 may be inserted orgenerally fixedly placed in connection with the base unit 180 in aregion 185 of the base unit, such a docking station. In some cases,there are structures (e.g., guide pins, guide slats, guide holes, guideslots, or structures shaped like opposing puzzle pieces) to assist withaligning the removable system (or removable airway) 179 with the baseunit 180. The removable system (or removable airway) 179 may be largeror smaller than region 185 of the base unit. For example, removablesystem (or removable airway) 179 may be larger than region 185, and theinlets and outlets of removable system (or removable airway) 179 mayextend past the boundaries of region 185. In another example, removablesystem (or removable airway) 179 may be smaller than region 185 suchthat removable system (or removable airway) 179 fits within region 185.In such cases, the ports (i.e., the inlets and outlets) of removablesystem (or removable airway) 179 may include bent (e.g., 90 degree)sections such that connections may be made to the ports of the removablesystem from above.

The removable system (or removable airway) 179 may be configured to beremovable from the base unit 180. Removable system (or removable airway)179 may be removed to be cleaned or to be disposed of and subsequentlyreplaced with a new removable system (or removable airway) 179 or acleaned removable system (or removable airway) 179.

The removable system (or removable airway) 179 may further be configuredto be cleaned in place (e.g., the removable system (or removable airway)179 may be configured to be removable and cleaned in place, or thesystem may not be configured to be removable). The capability to becleaned may be enabled by the isolation of the airway from the baseunit, and its size and shape as described above.

In some embodiments the isolated removable system (or removable airway)179 is removable. In some embodiments, the removable system (orremovable airway) 179 is disposable (e.g., between patients). In someembodiments, the removable system (or removable airway) 179 iscleanable. These embodiments are not mutually exclusive.

In some embodiments, the removable system (or removable airway) 179 maycontain sensors. Sensors may be for pressure and or flow. The sensorsmay be active, such as powered by electricity. If the removable systemcontains sensors, then the removable system may have connectors on theremovable system that mate to connectors on the base unit 180. Theconnectors may be electrical. Electrical connections may also benon-contact. Power to the sensors may be wireless such as by the Qistandard or other radiative or inductive means. Communication to thesensor may be wireless or wired, such as by WiFi or Bluetooth.

In some embodiments, the removable system (or removable airway) 179 mayhave regions or systems that together with a related system in the baseunit 180 form a sensor system. In some embodiments, the regions orsystems in the removable unit are passive, in that they do not containany active components, such as electronics or sensors that receiveelectrical power.

FIG. 20 is a simplified schematic of an example of a sensor withportions in the removable system (e.g., removable system (or removableairway) 179 in FIG. 19) and in the base unit (e.g., 180 in FIG. 19) , inaccordance with some embodiments. In FIG. 20, subsystem 196 of theremovable unit 192 forms a first portion of a sensor. Subsystem 196 hasinlet 194 and outlet 195 that couple the subsystem 196 to othercomponents of the removable system. Subsystem 197 in a base unit 193forms a second portion of the sensor such that the two subsystems form asensor system. That is, the subsystems 196 and 197 together form asensor, for example, to measure pressure and/or flow. The method ofinteraction between the two subsystems 196 and 197 may be electrical,optical, mechanical, or other means of interacting. Each subsystem 196and 197 comprises components which on their own do not function as asensor, but when combined form a system that is able to sense a desiredproperty. A sensor can have an output signal that is predictably relatedto a property (e.g., pressure or flow) of a system. The output signalmay be electrical (either analog or digital), optical or mechanical.

In some embodiments, the subsystem 196 in the removable unit 192 has ameans for allowing light to enter the airway, such as a transparentwindow, such as glass, quartz, or plastic, or an optical filter or lens.The subsystem 196 may also have a plurality of windows or other passiveoptical components such as mirrors, lenses, and gratings.

In some cases, the complexity of the removable unit 192 (or removablesystem (or removable airway) 179 in FIG. 19) is minimized, for example,to minimize cost of a potentially disposable removable unit.

Active components such as pressure and flow sensors may be incorporatedinto subsystem 196. For example, a heat source (e.g., a hot wire) and atemperature sensor (e.g., a thermistor) may be disposed in subsystem196, and subsystem 196 may have external electrical connections to amating part on the base unit, to enable what is generally known ashot-wire anemometry. In another example, pressure sensors (e.g., MEMSsensors) may also be disposed in subsystem 196, and subsystem 196 mayhave external electrical connections that mate to a base unit.

In some embodiments, ultrasonic flow sensors may be arranged to measureflow within the airway in the removable unit. In some embodiments usingultrasonic flow sensors, there are no active components in the subsystem196. The subsystem 196 may contain tubing, and optionally a means (e.g.,a slot, or a pin, or other alignment structure) to fixedly couplesubsystem 196 to the ultrasonic source and sensors in the base unit 193.The tubing may be metal, plastic, or other suitable material fortransmitting ultrasound.

In yet another embodiment, flow within subsystem 196 (that is part ofremovable unit 192) may be measured with optics in the subsystem 197(that is part of the base unit 193) such as by interferometry or by aSchlieren-type shadowgram (e.g., using Schlieren photography, orshadowgraphs). Such systems measure flow that is related to disturbancesin the airway such as turbulence or induced Karman vortices. Suchsensors could include an optical system (e.g., including a light sourceand a detector, where the detector is an array of photodetectors, or acamera (e.g., a CCD camera)) in the subsystem 197, and one or morewindows for light to enter and exit an airway within subsystem 196containing a flowing gas, as described herein.

In yet another embodiment, flow may be measured by a mechanical means inthe subsystem 196, such as using a paddle wheel or turbine. Air flowmakes the wheel or turbine rotate. The movement of the paddle wheel orturbine can be measured by external (e.g., in the subsystem 197) lightsource and detector means (e.g., an electric eye, as described herein),whereby the paddle wheel interrupts of changes the intensity of thelight impinging upon a part of the rotating part such that a detectordisposed to receive light measures a change in intensity as the rotatingpart moves. The light may be reflected, refracted, diffracted, or passthrough in such a position that it is interrupted and then notinterrupted periodically. The rate of the changes in intensitycorrespond to the speed of the rotating means and the flow rate.

In some embodiments, pressure may be measured by deformation of asurface of the airway in subsystem 196. The deformation may occur withina region that has a lower compliance than the surrounding regionenclosing the airway such that when the pressure in the airwayincreases, the softer (or compliant) region pushes outwards.

FIGS. 21A-21B are simplified schematics of an example of an airway witha compliant region, that can be a component of subsystem 196 in someembodiments. In FIG. 21A, an airway 202 contains a compliant region 198.When pressure 200 is the same inside and outside the airway, the region198 is in a relaxed state (e.g., flat, or other geometries). When thepressure 201 is greater than the pressure outside the airway (generallyatmospheric pressure), the region 199 (or a portion of region 199)distorts. This distortion can be measurable using different means ofmeasuring a change of the compliant region, such as optically,electrically, and or mechanically. For example, the distortion could bemeasured by bouncing a light source off the distorted region anddetecting a change in the magnitude or position of the reflected light.In another example, the distortion could be measured by detecting achange in capacitance between an electrically conductive portion of thedistorted region and a second electrically conductive surface, that isfixed in a proximity to the electrically conductive portion of thedistorted region 199. The configuration of the electrically conductiveportion of the distorted region 199 and the second electricallyconductive surface can be configured such that a desired change inpressure is sufficient to cause a measurable change in capacitance. Inanother example, the distorted region 199 could be measured electricallysuch as by coupling a strain gage to the distorted region, and couplingelectrical connections from the strain gage to a means to detect achange (e.g., in resistance) of the strain gauge. Other strain gaugessuch as fiber optic strain gauges may also be used to detect thedistortion of region 199. In some cases, the deformable region 198 maycontact a mechanical pressure gage, such as the surface of a Bourdontube.

FIGS. 22A-22B are simplified schematics of an example of a pressuresensor, in accordance with some embodiments. In FIG. 22A, the compliantregion 206 contacts a force-measuring means 207 that may be a componentof the subsystem 197. That is, the force-measuring means 207 may be partof and fixed within the base unit 193. When the subsystem 196 isremoved, the subsystem 209 (corresponding to subsystem 196) is removedand is no longer in contact with the force-measuring means 208(corresponding to subsystem 197). When the pressure 205 increases beyondatmospheric pressure the region 206 presses on the force-measuring unit207. The force measured by the force-measuring unit 207 can becalibrated to read out in any unit system (e.g., by a control system),such as cmH₂O. The force-measuring unit 207 may contain a strain gage asin a scale system, or other load cell. The force-measuring unit 207 maybe placed in contact with the compliant region 206 such that atequilibrium pressure between the inside and the outside of the airway, apositive force is measured by force-measuring unit 207. In some cases,force-measuring unit 207 may be coupled (e.g., reversibly so it may bedecoupled when the removable unit is removed, for example, using amagnetic coupling, an electromagnetic coupling, a clip, a pin and an eyehole, an adhesive, or other reversible mechanical connection means) tocompliant region 206, such that negative pressure inside the airway withrespect to outside the airway may be measured. In some cases,force-measuring unit 207 may be coupled to compliant region 206, and bea part of subsystem 196. In some cases, a negative pressure inside theairway with respect to outside the airway may be measured using light(e.g., using a light source and detector that are part of the base unit193) to detect the movement of compliant region 206, as describedherein.

FIGS. 23A-23B are simplified schematics of an example of a pressuresensor, in accordance with some embodiments. In FIG. 23A the pressure216 inside tube 210 is the same as pressure 217 outside tube 210.Deformable region 211 is approximately flat, or undeformed, in thisexample, but may have other shapes in this equilibrium condition. Aportion of a load cell (or other force sensing means) 212 is in contactwith the deformable region 211 at the position shown. FIG. 23B shows thecase where the pressure inside the tube is higher than the pressureoutside the tube, where the deformable region 214 expands outward,pressing on the load cell (or other force-sensing means) 215. FIG. 23Bshows the load cell (or other force-sensing means) 215 moving to a newposition, where the position is measured by the force-sensing means.This measurement can be converted to a pressure in desired units. Theforce versus pressure may not be linear. In such a case, a system mayhave a look-up table or other means of storing the relationship betweenforce and pressure such as by a curve fit formula to convert themeasured force to a pressure.

In some embodiments, flow of a gas (e.g., air, or oxygen mixed withother gases, or a gas with other materials such as solid or liquidparticles) within a removable airway (e.g., 192 of FIG. 20) can bemeasured using sound produced by the moving gas.

In some embodiments, the gas flow within a removable airway (e.g., 192of FIG. 20) can be measured by detecting the level of sound made by thegas (e.g., air) moving in the tube. In general, the microphone (used asa term for a sensor that converts sound waves to an electrical signal,or to another detectable signal that is not sound, such as to light) iscompletely outside the tube and is contained in the subsystem 197.

FIG. 24 is a simplified schematic of an example of a flow sensorcontained within the base unit (e.g., 180 in FIG. 19), in accordancewith some embodiments. A tube 218 (e.g., that is part of removablesystem (or removable airway) 179 in FIG. 19) may have a gas (e.g., air)219 flowing in it. The gas causes a sound 220 to be emitted from thetube, detectable outside the tube via a microphone 221, which convertsthe sound 220 to an output signal on the wires 222. The output signalcan then be provided to a control system (as described herein) forcontrolling different components (e.g., valves configured to variablyadjust the flow of gas through the valve) of the ventilator.

In some cases, the tube 218 may be a portion of the flow sensor that isa part of the removable system (e.g., removable system (or removableairway) 179 in FIG. 19), and microphone 221 is a portion of the flowsensor that is a part of the base unit (e.g., 180 in FIG. 19). Forexample, tube (or section of tube) 218 may be configured to permit soundto pass through a wall of the tube, such that the sound generated by theflowing gas within the tube may be efficiently transferred to microphone221 located outside of tube 218. Tube 218 may be configured to permitsound to pass through a wall of the tube, for example, by tube 218 beingmade of a material that allows sound to pass through it (e.g., silicone,vinyl, plastic, or metal), and/or by including structures within tube218 that increase the intensity of sounds generated by a flowing gas.Additional examples of acoustic flow sensors with portions that are partof the removable system (e.g., removable system (or removable airway)179 in FIG. 19) and that are part of the base unit (e.g., 180 in FIG.19) are described herein.

FIG. 25 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system (e.g., removable system(or removable airway) 179 in FIG. 19) and that are part of the base unit(e.g., 180 in FIG. 19), in accordance with some embodiments. The wall ofthe tube 223 may have a region (or diaphragm) 224 that is of a materialdisposed to transmit sound 225 more easily than the walls of the tube.Tube 223 and region 224 may be part of a removable system (e.g.,removable system (or removable airway) 179 in FIG. 19). This region 224in may be a thin diaphragm (e.g., made of plastic). Such a diaphragm 224may be similar to those found on the faces of stethoscopes or speakers.The diaphragm 224 is fixed around its edges to the tube 223. In somecases, tube 223 may have a flat region adjacent to diaphragm 224, suchthat diaphragm 224 may have a circumference that lies in a flatnon-curved plane. The diaphragm 224 may also be curved or haveundulations in it (e.g., allowing for greater movement). The soundemitted from the diaphragm 224 can then be detected using microphone221, which converts the sound 225 to an output signal on the wires 222,as described above.

In other embodiments, the flow rate within tube 223 may be detected byplacing an accelerometer (not shown) against the diaphragm 224. Thesupport and connection to the base unit would generally have a lowercompliance than the diaphragm.

FIG. 26 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system (e.g., removable system(or removable airway) 179 in FIG. 19) and that are part of the base unit(e.g., 180 in FIG. 19), in accordance with some embodiments. FIG. 26shows the microphone 229 in the base unit (e.g., corresponding tosubsystem 197) enclosed in a cone 228. The cone 228 may contact the tube227 and surround the sound-transmitting region (e.g., diaphragm) 226. Insome cases, the tube 227 is not mechanically connected to the soundgathering means (or cone) 228 cone and microphone 229. Thus, the tube227 may be separated from the sound detecting means (228 and 229), andsubsequently the same (or similar) tube 227 be placed back in contactwith the sound detecting means (228 and 229). In a ventilator, the sounddetecting system (228 and 229) may be part of the base ventilator unitand the tube is part of the disposable airway system.

FIG. 27 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system (e.g., removable system(or removable airway) 179 in FIG. 19) and that are part of the base unit(e.g., 180 in FIG. 19), in accordance with some embodiments. A tube 230may also have disposed within it or as a part of it as a system, a soundgenerating subsystem 232, which has gas (e.g., air) 231 impinging uponit. The sound generating subsystem 232 is designed to generate soundwhen gas 231 impinges on it, converting some of the energy of theflowing gas 231 to sound. This may have the beneficial effect ofincreasing the amount of sound generated in tube 230 for detection. Thesound emitted from the sound generating subsystem 232 can be detectedusing microphone 221, as described above.

FIG. 28 is a simplified schematic of an example of a flow sensor that iscontained within the removable system (e.g., removable system (orremovable airway) 179 in FIG. 19), in accordance with some embodiments.In FIG. 28, microphone 234 a may be disposed within the tube 233 that ispart of the removable system. In some cases, wires 234 b carrying anoutput signal from the microphone pass in a sealed fashion through thewalls of the tube 233 to connect with a control system that can displayor otherwise make use of the sound output signal (as described herein).

FIG. 29 is a simplified schematic of a flow sensor that is a part of theremovable system (e.g., removable system (or removable airway) 179 inFIG. 19), or with portions that are part of the removable system (e.g.,removable system (or removable airway) 179 in FIG. 19) and the base unit(e.g., 180 in FIG. 19) , in accordance with some embodiments. FIG. 29shows a flow detector system with more than one microphone (2 in thiscase, but there could be more than 2 in other cases), such that flow indifferent directions may be detected differently thus indicating flowdirection. A tube 235 may have a first structure 238 and a secondstructure 239. In some cases, structures 238 and 239 are microphones,where microphone 238 may be more sensitive to sound 236 coming from adirection opposite to a sound 237 which may be more easily detected by amicrophone 239. The microphones may be placed in any direction whichenables them to have an asymmetric sensitivity to flow direction.

FIG. 29 also shows microphones 221 and 221 b, that are located outsideof tube 235, and may be the base unit (e.g., 180 in FIG. 19). In somecases, structures 238 and 239 are sound generating subsystems (e.g.,subsystem 232 in FIG. 27). These sound generating structures 238 and 239may be disposed to generate sound from flow more from one direction thananother, and microphones 221 and 221 b can be used to detect thedirection of the flow. Sound generating structures 238 and 239 may alsogenerate different sounds, such as sounds of different frequencies,where one sound generator may generate a tone if gas (e.g., air) comesfrom one direction and a second sound generator generates a sound comingfrom the opposite direction with a different tone than the firstgenerator and a single microphone (e.g., 221, located outside of thetube 235) which output a signal which can then be processed to determinethe tone and in this way determine which generator produced the soundand thus which direction the flow was from. Such tones may also beproportional to flow, so the frequency (or ratio frequencies, orfrequency spectrum) of the sound may be used to determine flow rate. Thesound emitted from the sound generating subsystems 238 and 239 can bedetected using microphones 221 and 221 b, as described above.

FIG. 30 shows a simplified schematic of an example of a structure withina tube that may generate sound that can be detected by a microphone of aflow sensor, and the frequency spectrum of the sound that is processedto determine a flow rate of the gas (e.g., air), in accordance with someembodiments. The acoustic flow sensors described herein may detectsounds (generated by a flowing gas) in any frequency range where amicrophone operates, for example from less than 100 Hz to greater than20 kHz, or from 100 Hz to 20 kHz, or from 1 kHz to 20 kHz, or from about20 kHz to about 40 kHz, or at about 10 kHz. The higher frequencies, suchas those above 20 kHz, may be advantageous because there tends to belittle ambient noise in this region so there is less ambient noise tointerfere with the operation of the sensor. FIG. 30 shows a tube systemthrough which gas (e.g., air) flows that may generate sounds which havea detectable harmonic content. That is, the sound may not becharacterized as noise, such as white noise, but may have certainfrequencies with an amplitude larger (or much larger) than thebackground. Orifice 259 is smaller than the tube 239 into which gasflows, which can preferentially generate certain sound frequencies. Inthis example, tube 239 with gas (e.g., air) 240 generates a sound 250which has a trace versus time 251 with a frequency spectrum 252 whereone or more peaks are present. The peaks in frequency may be detectedand their amplitude correlated with flow rate, such as by taking aFourier transform or other mathematical transform that converts fromtime domain to frequency domain, by the use of filters, or by a lock-intechnique. The tube system may be designed to generate a specificfrequency. Advantageously, the frequency would be a high frequency abovewhere most ambient sounds are, such as in a hospital, where generallythere is not much sound above 10 kHz or 20 kHz. Additionally, using anorifice 259 may generate greater sound levels for the same flow ratethan tubes without such an orifice 259.

Alternatively, a subsystem such as 232 in FIG. 27 could preferentiallygenerate sounds at certain frequencies, and the sound can be analyzed inthe frequency spectrum as described above, to make the flow detectorless susceptible to errors caused by ambient noise. For example, thesubsystem 232 in FIG. 27 may be a reed or a whistle. A reed used in theflow sensors described herein may be a structure designed to vibratewhen gas (e.g., air) passes over it, such as in a clarinet, thustransducing flow energy to sound energy. In some cases, a flow sensordescribed herein may use two or more, or a plurality of, reeds. The twoor more reeds may generate the same tone spectrum or different tonespectrums, or generate different tones at different flow rates. Thesound generating subsystem 232 may also be a whistle (e.g., a structurethat passes flowing gas (e.g., air) across its own path to create aresonance which is a vibration of compression in the gas which isconverted to sound).

FIGS. 31A-31B are simplified schematics of a flow sensor with portionsthat are part of the removable system (e.g., removable system (orremovable airway) 179 in FIG. 19) and the base unit (e.g., 180 in FIG.19), in accordance with some embodiments. FIG. 31A shows a flow sensorincluding regions 254 and 255 surrounding the flow detection regionwithin tube 253, and microphone 258. Regions 254 and 255 may include oneor more structures that insulate the sound detection region from soundsources external to the sound detecting region. For example, a structurein regions 255 may include sound insulating materials such as fiberglassinsulation, STYROFOAM™, polymer foams, metals, or laminates (e.g.,having alternating impedance to sound transmission). FIG. 31B shows anexample of a region 254. In some cases, regions 254 may include a tube256 (that couples with tube 253 in FIG. 31A) and structures (e.g.,baffles) 257 in a zigzag pattern, that can block sound yet still let gas(e.g., air) flow freely. In some cases, the microphone 258 may also beinsulated with materials and/or structures (not shown) from soundsources external to the sound detecting region. The regions 254 and/or255 may be part of the removable system (e.g., removable system (orremovable airway) 179 in FIG. 19) and/or part of the base unit (e.g.,180 in FIG. 19). The tube may include a diaphragm (not shown) that ispart of the removable system (e.g., removable system (or removableairway) 179 in FIG. 19). The microphone 258 may be part of the base unit(e.g., 180 in FIG. 19), or may be affixed to and be a part of theremovable system (e.g., removable system (or removable airway) 179 inFIG. 19).

The microphone(s) of the flow detectors described herein (e.g., in FIGS.14, and 20-33E) may have a gain that is adjustable in real time inresponse the changes in sound amplitude. In some embodiments, the gainis high for low levels of sound, and the gain is low for high levels ofsound. In some embodiments, the output signal from the microphone has anapproximately constant amplitude, and the gain is continually adjustedto keep the output signal amplitude approximately constant, such thatthe output signal is the gain, and the gain is then correlated withsound level. In this manner, a microphone used in the flow sensorsdescribed herein may have an increased dynamic range.

In a ventilator, the flow rate detected is generally in the range ofless than 1 liter per minute up to 60 liters per minute, or up to 100liters per minute. Flow detection by sound can be very sensitivecompared to turbines or hot wire anemometers, with a fast response timesas well. Flow rates may be detectable at 0.1 liters per minute in tubesof generally about 25 mm diameter. This is a very slow movement of gas,of about 3 mm per second. Further, in the flow region of 10-50 litersper minute or 1-60 liters per minute, the flow rate versus amplitude ofsound generated may be approximately linear (in some tubes). In somecases, the amplitude of sound generated decreases above a certain flowrate, which may also be advantageously used to detect a certain flowrate with a high sensitivity as the fall off is greater than the rise atlower flow rates.

FIG. 32 is a simplified schematic of an example of a flow sensor withportions that are part of the removable system (e.g., removable system(or removable airway) 179 in FIG. 19) and the base unit (e.g., 180 inFIG. 19), in accordance with some embodiments. FIG. 32 shows a flowsensor that uses optical means to detect sound generated in a tube. Atube 260 with gas flowing in it may cause a diaphragm 261/262 to vibratebetween positions 261 and 262. A light beam 263 generated by a lightsource 264 may impinge upon the surface of the diaphragm and bereflected into a detector 265. The intensity and/or position of the beamat the detector may be transduced into a signal proportional to thesound or movement of the diaphragm, such as with a photodiode capable ofmeasuring the intensity of the beam 263, or a light sensor capable ofmeasuring the position of beam 263 (e.g., a split photodiode, array ofphotodiodes, or an image sensor such as a camera). The light source 264may be a laser, an incandescent lamp, or an LED. The diaphragm 261/262may be part of the removable system (e.g., removable system (orremovable airway) 179 in FIG. 19), and the light source 264 and detector265 may be part of the base unit (e.g., 180 in FIG. 19).

FIGS. 33A-33E are simplified schematics of portions of flow sensors thatmay be used in flow sensors that are contained in the removable system(e.g., removable system (or removable airway) 179 in FIG. 19), or thathave portions that are part of the removable system (e.g., removablesystem (or removable airway) 179 in FIG. 19) and the base unit (e.g.,180 in FIG. 19), in accordance with some embodiments. The tube of a flowsensor, or a deformable region of the tube, may have shapes andgeometries other than planar. For example, one or more structures mayextend into the tube or protrude from the tube, such that flow withinthe tube impinges on the structure(s) and generates sound. FIGS. 33A-33Dshow examples of different structures 266 a-e extending into orprotruding from the tube 267 a-e of a flow sensor. FIG. 33A shows astructure 266 a that includes a pointed groove or conical indentextending into the tube 267 a. FIG. 33B shows a structure 266 b thatincludes a rounded indent extending into the tube 267 b. FIG. 33C showsa structure 266 c that includes a narrow indent (or pillar) extendinginto the tube 267 c. FIG. 33D shows a structure 266 d that includes aplurality of one or more rods or slats of the same or differentgeometries extending into the tube 267 d. FIG. 33E shows a structure 266e that includes a region protruding from tube 267 d. The tube may have aplurality of sound-generating structures (e.g., 266 a-e as shown inFIGS. 33A-33C), and/or a plurality of microphones (not shown) to detectthe sound from the structures 266 a-e. The sound generating structure(s)(e.g., 266 a-e) may be located within one or more sound generatingregions of the tube (e.g., 267 a-e). The sound generating region(s) maybe in more than one location within the tube, and/or may surround thetube. The sound generating region(s) may be a section of the tube suchas a thin section such that sound is emitted generally radially outwardsall around the tube. A chamber may be disposed around the tube tocollect sound from many directions emitted by the tube.

The flow detectors described herein (e.g., in FIGS. 14, and 20-33E) maybe, or have portions that are, a stand-alone unit that can be connectedto an inlet and an outlet tube or pipe.

The flow detectors described herein (e.g., in FIGS. 14, and 20-33E) maybe a system that is, or have portions that are, fixedly couplable (orattachable) to a tube or pipe, such as via a clamp.

The flow detectors described herein (e.g., in FIGS. 14, and 20-33E) mayhave a means to calibrate the detected sound to a flow rate, such flowrate measured by a preconfigured and calibrated detector system. Thedetector may have adjustments or inputs of calibration data or settings.

In some cases, the acoustic flow sensors described herein (e.g., inFIGS. 14, and 20-33E) may also measure other parameters of a flowinggas, such as pressure and/or temperature. In some cases, the acousticflow sensors described herein (e.g., in FIGS. 14, and 20-33E) may workin conjunction with another one or more sensors that measure otherparameters of a flowing gas, such as pressure and/or temperature. Aprocessor (e.g., that is part of the control system) may convert thedetected sound (e.g., intensity and/or frequency) and another detectedparameter (e.g., temperature and/or pressure) to a flow rate of the gas.In some cases, a measured flow rate of a gas and another detectedparameter (e.g., temperature and/or pressure) can be used by the controlsystem to convert a gas flow rate to an amount of gas (e.g., air, oroxygen) moving past (or through) the sensor (or moving within a tube).In some cases, the total amount of gas moving through the sensor systemmay be calculated from inputs from independent flow, pressure, andtemperature sensors.

FIGS. 34A-34C are simplified schematics of an example of a ventilatorsystem with a removable airway, in accordance with some embodiments.FIG. 34A is a top view of a ventilator base unit section 270 (e.g., baseunit 180 in FIG. 19) into which a removable unit may be inserted. FIG.34B is a bottom view of a removable unit 286 (e.g., removable system (orremovable airway) 179 in FIG. 19) that can be inserted onto the baseunit section 270 in FIG. 34A. FIG. 34C is an isometric view of both thebase unit 295 (e.g., containing portion of base unit 270 in FIG. 34A)and the removable unit 304 (e.g., 286 in FIG. 34A). The control of flowwithin the removable unit 286 (or 304) is via pinch valves, where thepinch valves include a roller 273 or 274 (or other means such as aplunger), where the roller 273 or 274 (or plunger, or other means) isconfigured to compress a flexible tube of the removable unit 286 (or304). The pinch valve may have multiple movable elements which may incombination compress a tube, such as two opposing elements with a tubein between where both elements move towards each other to close a gapbetween them thus compressing the tube, such as in a scissor mechanism.

In some embodiments, the rate of flow within the removable unit 286 (or304) may be controlled by controlling how much a pinch valve compressesa tube of the removable unit 286 (or 304), and how much of aconstriction is formed within the tube. The tube may be closed off withsufficient pressure from the pinch valve to constrict the tubecompletely. The flow sensors may be positioned downstream of the valveon the inhale side, and upstream of the valve on the exhale side. Theremovable unit 286 (or 304) may have two airways, one for inhale and onefor exhale, that may be linear or straight tubes. At the ends of thetubes may be connectors for gases. The tubes may be mounted on a plateor other means that keeps the tubes in a fixed relative position. Theremovable unit 286 (or 304) may fit into the portion of the base unit270 (or the base unit 295) in a predetermined location with only onepossible orientation with suitable mating portions (e.g., pins, slats,holes, slots, structures that fit together in the manner of puzzlepieces) on the portion of the base unit 270 (or the base unit 295) andremovable unit 286 (or 304). The removable unit 286 (or 304) may alsolock or snap into place, or have a clasp that is automatically ormanually engaged when the disposable is manually installed in theportion of the base unit 270 (or the base unit 295). The air inlets andoutlets of removable unit 286 (or 304) may be tapered to mate withstandard ventilator airway components, such as a patient circuit (i.e.,the tubes that connect a ventilator to the trachea tube or mask of apatient), or filters. A connector on the inhale side of the removableunit 286 (or 304) may be of a type to connect to an air supply, such asa hospital air supply. The valves may have a roller that can press on atube of removable unit 286 (or 304), and a rib (e.g., between twovalves) to back the tube when it is pressed on. The flow and/or pressuresensors (or first portions thereof) may be mounted in the portion of thebase unit 270 (or the base unit 295) facing upwards so as to measureflow within removable unit 286 (or 304), and/or so as to mate withsecond portions of the sensors (e.g., diaphragms) on the removable unit286 (or 304).

While other types of sensors and configurations of valves are possible,as described above, FIGS. 34A-34C show one example ventilator system. Aportion of a base unit 270 has two rotatable arms 271 and 272. On theends of arms 271 and 272, extends rollers 273 and 274. Between rollers273 and 274 is a wall or rib 275 (that may be non-flexible, or havelimited flexibility), such that a tube of the removable unit 286 whenplaced between the roller and the rib may be compressed. Each valvecontains a rotatable arm 271 or 272, a roller 273 or 274, and the wallor rib 275. The valves shown in FIGS. 34A-34C may be configured tovariably adjust the flow of gas through the valve (i.e., through tube290 a or 290 b passing through the valve, or through a compressiblesection of a tube 290 a or 290 b passing through the valve), asdescribed herein. For example, each rotatable arm 271 and 272 may have aplurality of positions configured to compress tube 290 a or 290 b (or tocompress a compressible section of tube 290 a or 290 b) by varyingamounts. The portion of the base unit 270 also contains microphones 276and 277, that are configured to mate with the associated components 280and 281 of the removable unit 286 (shown in FIG. 34B) to form a flowsensor. The portion of the base unit 270 also contains force sensors(e.g., load cells) 278 and 279. The force sensors 278 and 279 areconfigured to mate with the congruent parts (e.g., compliant regions)282 and 283 of the removable unit 286 (shown in FIG. 34B) to form apressure sensor to detect the pressure in the airway of the removableunit 286. In some cases, the ventilator system in FIGS. 34A-34C maycontain one or more blow-off valves that open in response to a maximumpressure being detected in the inhale and/or exhale lines.

The portion of the base unit 270 (or the base unit 295) and theremovable unit 286 (or 304) may have a system that aligns the two uponinsertion, and also allows insertion only in a particular orientation,such as a square protrusion on the base 284 and a square hole on thedisposable 285. Many other lock and key systems are possible. Forexample, the shape of the plate on the removable unit 286 (or 304) maybe such that it fits into the portion of the base unit 270 (or the baseunit 295) in a single orientation.

The removable unit 286 (or 304) may include two airways, inhale line orairway 287 and exhale line or airway 288 that are not connected to eachother. The inhale line or airway 287 may have a connector 289 to a gassource. Tubes 290 a and 290 b that are flexible tubes, and may havediameters smaller than the diameter of the patient circuit (e.g.,smaller than around 20 mm to 25 mm in diameter), such that a the innerdiameter of tubes 290 a and 290 b are from 2 mm to 6 mm, or smaller than10 mm. Tubes with small diameters (e.g., less than 10 mm), may allow forgreater control of the flow within inhale line or airway 287 and exhaleline or airway 288, when air from a high-pressure source is used. Thetube 290 a connects to a section 291 a (where section 291 a may have alarger diameter than tube 290 a). Section 291 a may have lowerflexibility than tube 290 a, and contains the mating portions of theflow sensor (e.g., a diaphragm) 280, and pressure sensor (e.g., acompliant region) 283. In some embodiments, there are no openings aroundthe mating portions of the flow sensor (e.g., a diaphragm) 280, oraround the mating portions of the pressure sensor (e.g., a compliantregion) 283. Therefore, there is no opening (or port) for air (or airwith other matter, such as particles) to escape inhale line or airway287 and exhale line or airway 288 of the removable unit 286 other thanthrough the dedicated ports 289, 294, 292, and 293. The air withininhale line or airway 287 can exit through a connector portion (or port)292, which may be tapered to match a tube of a patient circuit. Theexhale line or airway288 has a similar inlet (or port) 293, which alsomay be tapered to match a tube of a patient circuit (although, in somecases port 293 may be of a different dimension than port 292 in theinhale line to prevent misconnecting inhale and exhale patient circuitlines (or tubes)). The exhale airway288 may have an exit connector (orport) 294 that may be tapered to mate with other ventilator components.For example, port 294 may connect to a filter or other air cleaningmeans, such as thermal or UV sterilizers (e.g., to filter out particlesor infectious material before they are expelled to the atmosphere). Theinner diameter of the components of exhale line or airway 288 may besimilar to that of a patient circuit exhale line (and/or an endotrachealtube) to allow for minimal restriction of exhale flow between thepatient circuit exhale line and the ventilator exhale line or airway288. Thus the inner diameter of section 291 a may be between 15 mm and25 mm. The inhale line or airway 287 may be of any advantageous diameterto achieve control of flow and pressure.

FIG. 34C shows base unit 295 having a region 296 (which is the same as,or similar to, portion of base unit 270 in FIG. 34A) that accepts aremovable airway unit 304 (which is the same as, or similar to,removable unit 286 in FIG. 34B). Region 296 includes components ofadjustable pinch valves 297 and 298 with fixed means (e.g., plate) 303,microphones 299 and 300, and force sensors 301 and 302. Valve 297 and/or298 may be configured to variably adjust the flow of gas through thevalve (i.e., through a tube passing through the valve, or through acompressible section of a tube passing through the valve), as describedherein. The removable airway 304 is inserted generally along a path 303into the base unit region 296. Alignment means 305 and 306 are shown asa protruding prism 305 that mates with hole 306. The base unit may havea means of human interaction region 307, for example a touch screen, adisplay, a control panel, or other user interface (e.g., with buttons,knobs, sliders etc.). The ventilator system shown in FIG. 34C may alsohave wireless communication, such as via WiFi or Bluetooth, and connectto a human interaction interface on a separate device (e.g., a remotecontrol, computer, smartphone, or tablet) that may view the status ofthe ventilator and/or control it.

The region 296 is shown on the top of the base unit 295 in FIG. 34C,however, in other embodiments, region 296 may be on a different surfaceor orientation of a ventilator base unit, such as at the back, or on thesides, or underneath. The shape of the tubes in the removable unit 286or 304 may be straight as shown in FIGS. 34B and 34C, or may have rightangles, or have other angles, or be curved. In some embodiments, theconnectors may be at right angles to the plane 308 (on the top of theremovable unit 304) such that the removable unit 304 may be inserted ina region the base unit (smaller or larger in area than the removableunit 304), such that the tubes of the removable unit 304 can beconnected (e.g., to an air supply, a patient circuit, and/or a filter)in a perpendicular direction from the base unit 295.

The ventilator systems shown in FIGS. 34A-34C may incorporate additionalvalves and sensors, or may have fewer valves and sensors than shown inthe figures.

For example, an additional pressure sensor may be disposed upstream ofthe inhale valve to measure the pressure in the inhale line or airway287 when the valve is closed. This may help to adjust the valve for apredetermined flow when it is opened, especially when the pressureupstream of the valve changes when the valve is closed, so that theposition the valve had been in to achieve a set flow will now bedifferent when the valve is open. Using the pressure in the upstreamline may help to predetermine a setting of the valve on the subsequentcycle. It may, for example, yield a starting point for the valveposition that will be closer to a valve position setting that achievesthe desired flow, as the valve may be in closed-loop control with theflow sensor. An additional air inlet (or port) to inhale line or airway287 may be included such that there is one inlet for one for oxygen andone inlet for air or nitrogen. Thus, the removable unit 286 (or 304) mayhave a plurality of gas inlets. Additional valves (e.g., pinch valves)and sensors (e.g., oxygen sensors) may be disposed in the system for thepurpose of mixing of the gases from multiple gas inlets in the inhaleline or airway 287. For example, an optical luminescence type of oxygensensor could be used, such that oxygen can be sensed without a port thatexposes the air within the inhale line or airway 287 to the sensor. Forexample, the luminous material of an oxygen sensor may be mounted in theinhale line or airway 287 of the removable unit 286 (or 304), and thesource and sensor components can be mounted in the base unit 270 (or295).

A system with fewer sensors than the systems shown in FIGS. 34A-34C mayhave no sensors on the exhale line. Volume control may be achieved bymeasuring the inhaled delivered volume (tidal volume) (e.g., using aflow meter in the inhale line), and the exhale valve can be used tomaintain PEEP (e.g., using a pressure sensor in the exhale line). PIP(peak inspiratory pressure) may also be controlled by the sensors in theinhale line or airway 287. In this way, a volume may be delivered, andthe PEEP controlled, such that as long as the PIP and PEEP aremaintained, it may not be necessary to measure the exhaled volume.

In some embodiments, the inhale lines or airways (e.g., 287) may have aconstant inflow or air and orifices that allow gas to escape (e.g., at agenerally fixed rate). Having a constant inflow of air into thedisposable may prevent material getting into the gas supply lines thuskeeping them clean. The orifices may be tubes that may be valved bypinching as described above. The tubes may have inner diameters from 0.1mm to 1 mm, or from 0.01 mm to 0.1 mm, or the tubes may have largerdiameters and each tube may contain an orifice with an inner diameterfrom 0.1 mm to 1 mm, or from 0.01 mm to 0.1 mm. In some cases, suchopenings in the inhale line or airway 287 are either closed, or whenopen have a gas flow exiting them. In some cases, these opening tubesmay be connected to the exhale exhaust such that some gas is alwaysflowing out the exhaust (from the inhale side) while connected to sourcegases.

The inhale line or airway 287 may also have a system comprising a regionthrough which the inhale gases (e.g., air, or oxygen mixed with air ornitrogen) flow that is a sterilizing region, such as by UV light or byheat, such as a region including a heated volume with temperatures from100° C. to 300° C. This region may sterilize incoming gases and any gasor matter that may move upstream into the gas sources.

The flow and pressure control of the ventilator systems shown in FIGS.34A-34C may be in open-loop or closed-loop control. If a system has apredetermined flow at a predetermined valve position, then open loopcontrol may be effective. More accurate control may be achieved wherethe valves are continuously adjusted in response to a measured flow, ameasured pressure, and/or another measured parameter, where continuallymeans a cycle of measure and adjust and measure and adjust. In somecases, the control system monitors pressure, and valves are opened andclosed in response to maximum and minimum pressure limits (e.g., PIP andPEEP thresholds).

The flow sensors of the ventilator systems shown in FIGS. 34A-34C may beaffected by the pressure within the inhale and exhale lines or airways287 and 288. That is, at a certain flow rate, the sensor may readdifferently at different pressures. A system may be calibrated such thatthe flow rate determined from a measurement of the flow sensor isconverted to a flow rate based on a generally concurrent reading of thepressure (measured using the pressure sensors), such as by using a lookup table or predetermined formula.

FIGS. 35A-35B are simplified schematics of examples of an inhale lineand an exhale line, respectively, of a ventilator system, in accordancewith some embodiments. The inhale line 35001 in FIG. 35A and the exhaleline 35002 in FIG. 35B, may be the same as or similar to the inhale lineor airway 287 and exhale line or airway 288 shown in FIGS. 34A-34C. Airinlet 1001 of inhale line 35002 in FIG. 35A may be coupled to an airsource (or to a source of oxygen mixed with other gases), which thenpasses through a tube 1002 to a variable valve 1003 (e.g., a pinch valveas described herein, for example, in FIGS. 3A-7, and 34A-34C). In somecases, air inlet 1001 is coupled to a gas source (e.g., air, or oxygenmixed with other gases), and the gas source is pressurized (e.g., atabout 50 psi). In some cases, the ventilator system may contain a pumpor compressor (e.g., in a base unit) to pressurize the gas before it isintroduced into air inlet 1001. The air exits variable valve 1003 andenters a manifold (or tube) section 1004. Pressure sensor 1006 (e.g., apressure sensor shown in FIGS. 21A-23B), flow sensor 1007 (e.g., anacoustic flow sensor shown in FIGS. 24-33E, and 34A-34C), and othersensors 1008 (such as a temperature sensor) are configured to measurepressure, flow, and other parameters (e.g., temperature) within tubesection 1004, as described herein. The tube section 1004 is connected toan air outlet port 1005 to which may be connected an inhalation line ofa patient circuit (and/or an endotracheal tube).

FIG. 35B shows an example of an exhale line 35002. An air expiratoryline of a patient circuit (and/or an endotracheal tube) that may beconnected to port 1009, which is connected to a section of a manifold(or tube) section 1013 with various sensors connected to it. Pressuresensor 1012 (e.g., a pressure sensor shown in FIGS. 21A-23B), flowsensor 1011 (e.g., an acoustic flow sensor shown in FIGS. 24-33E, and34A-34C), and other sensors 1010 (such as a temperature sensor) areconfigured to measure pressure, flow, and other parameters (e.g.,temperature) within manifold (or tube) section 1013, as describedherein. The sensing section of the manifold (or tube) section 1013 isconnected to a variable valve 1014 (e.g., a pinch valve as describedherein, for example, in FIGS. 3A-7, and 34A-34C) which is connected viaa tube 1015 to an exit port 1016. Exit port 1016 may include a filter(e.g., to remove or reduce the concentration of contaminants such asparticles and pathogens before air from the exhale line 35002 isexpelled into the atmosphere).

In some cases, the ventilator system in FIGS. 35A-35B may contain one ormore blow-off valves that open in response to a maximum pressure beingdetected in the inhale and/or exhale lines 35001 and 35002. The variablevalves 1003 and 1014 shown in FIGS. 35A-35B may be configured tovariably adjust the flow of gas through the valve (i.e., through tube1002 or 1015 passing through the valve, or through a compressiblesection of tube 1002 or 1015 passing through the valve), as describedherein.

Example Methods

In some embodiments, a method for using a ventilator system (e.g.,ventilator system shown in FIGS. 34A-34C and/or 35A-35B) includes thefollowing steps. An inhale valve (e.g., variable valve 1003 in FIG. 35A)may be opened to allow air (or a mixture of oxygen and other gases) toenter an inhale line (e.g., 35001 in FIG. 35A). In some cases, theinhale line is coupled to a gas source (e.g., air, or oxygen mixed withother gases), and the gas source is pressurized (e.g., at about 50 psi).In some cases, the ventilator system may contain a pump or compressor topressurize the gas before it is introduced into the inhale line. Thepressure, flow and/or other parameters (e.g., temperature) of the gaswithin the inhale line may be monitored using sensors (e.g., sensors1006, 1007 and 1008 in FIG. 35A). The inhale valve (e.g., variable valve1003 in FIG. 35A) may be controlled by a control system, and the controlsystem may be configured to receive measurement information from thesensors. The inhale valve (e.g., variable valve 1003 in FIG. 35A) may beopened to a predetermined position, or may be controlled in aclosed-loop feedback based on sensor measurements. The inhale valve(e.g., variable valve 1003 in FIG. 35A) may be configured to variablyadjust the flow of gas through the valve (i.e., through a tube passingthrough the valve, or through a compressible section of a tube passingthrough the valve). After the inhale valve is opened, air from theinhale line may be provided to a patient coupled to the inhale valve(e.g., via a patient circuit, and/or endotracheal tube), and thepatient's lung(s) may fill with the air.

As air is being provided to the patient, the pressure in the inhale linemay be monitored, and once a maximum PIP threshold is reached, then thecontrol system may close the inhale valve and open an exhale valve(e.g., variable valve 1014 in FIG. 35B) on an exhale line (e.g., 35002in FIG. 35B). After the exhale valve is opened and the inhale valve isclosed, then air may flow from the patient's lung(s) into the exhaleline, and out of an exit port (e.g., 1016 in FIG. 35B). While air isflowing from the patient to the exhale line (and out the exit port) thepressure in the exhale line may be monitored, and once a minimum PEEPthreshold is reached, then the control system may close the exhale valveand open the inhale valve on the inhale line. The exhale valve (e.g.,variable valve 1014 in FIG. 35B) may be configured to variably adjustthe flow of gas through the valve (i.e., through a tube passing throughthe valve, or through a compressible section of a tube passing throughthe valve). After the exhale valve is closed and the inhale valve isopened, then air from the inhale line may again be provided to apatient, and the method can continue as described above. Theinhale/exhale cycle described above may then be repeated many times(e.g., about 20 times per minute, for hours or days, or weeks).

In some cases of the above method, the control system may have one ormore predetermined user-settable or fixed delays, such as 1 second orless to 3 seconds or more, between any of the steps of the method. Thedelay may be zero in some cases. For example, after the PIP threshold isdetected, and after the inhale valve is closed, there may be a delaybefore the exhale valve is opened.

In alternative embodiments of the method above, flow may be used tocontrol the valves instead of, or in addition to, the pressure controlmethod described above. In some cases, temperature, flow and pressure,may all be measured and used to control the valves, instead of, or inaddition to, the pressure control method described above. For example,one or more of the flow and/or pressure and/or temperature sensorsdescribed herein, may measure parameters of a flowing gas, such as flowrate, pressure and/or temperature. A processor (e.g., that is part ofthe control system) may convert the parameters (e.g., flow rate,temperature, and/or pressure) to a flow rate and/or pressure of the gas,and the control system can then use the converted parameters to controlcomponents (e.g., valves) of the ventilator system. In some cases, ameasured flow rate of a gas and another detected parameter (e.g.,temperature and/or pressure) can be used by the control system toconvert a gas flow rate to an amount of gas (e.g., air, or oxygen)moving past (or through) the sensor (or moving within a tube). In somecases, the total amount of gas moving through the sensor system may becalculated from inputs from independent flow, pressure, and temperaturesensors. The valves of the systems operating in the above modes may alsobe configured to variably adjust the flow of gas through each of thevalves.

In some embodiments, a method for using a ventilator system (e.g.,ventilator system shown in FIGS. 1-2 and 15-16) includes the followingsteps. In a tidal volume inhalation control mode, a first valve (e.g.,valve 5 in FIG. 1) on an inhale line is opened and a second valve (e.g.,valve 9 in FIG. 1) on an inhale line is closed. The first valve may beconfigured to variably adjust the flow of gas through the valve. A firstbellows (e.g., bellows 7 in FIG. 1) positioned downstream of the firstvalve and upstream of the second valve inflates (e.g., due to the airpressure from a pressurized source) to a pre-determined volume, such as500 cc, from 50 cc to 1000 cc, or from less than 50 cc to more than 1000cc. When the predetermined volume has been reached, the control systemcloses the first valve and opens the second valve. Valves (e.g., 18 and23 in FIG. 2) on an exhale line may be open or closed during inflationof the first bellows. When the second valve opens, gas begins to inflatethe lung(s) of a patient, and pressure builds in a firstpressure-limiting subsystem (e.g., pressure-limiting andpressure-detection subsystem 11 in FIG. 1) coupled to the inhale line(e.g., downstream of the second valve). When pressure in the firstpressure-limiting subsystem reaches a predetermined value, or PIP (e.g.,about 30 cmH₂O, about 40 cmH₂O, or from 15 cmH₂O to 45 cmH₂O, or fromless than 15 cmH₂O to more than 45 cmH₂O), then the second valve isclosed by the control system, completing an inhale cycle. The firstvalve may then be opened to fill the first bellows to be ready for thenext inhale cycle of this mode.

When the second valve closes, the exhale cycle of this mode maycommence. The control system may have a predetermined user-settable orfixed delay, such as 1 second or less to 3 seconds or more, such thatvalve 18 may open after the delay has passed. The delay may be zero insome cases. When a third valve (e.g., valve 18 in FIG. 2) on an exhaleline opens, gas begins to pass from the lungs into a tube (e.g., tube 19a in FIG. 2) of the exhale line. In one mode, a fourth valve (e.g.,valve 23 in FIG. 2) on the exhale line may be closed during a firstportion of the exhale cycle. A subsystem (e.g., subsystem 20 in FIG. 2)maintains the pressure at or above a preset value (e.g., about 5 cmH₂O,or from 2 cmH₂O to 15 cmH₂O, or from less than 2 cmH₂O to more than 15cmH₂O), and a second bellows (e.g., bellows 21 in FIG. 2) on the exhaleline fills with exhaled gas from the patient. Gas may also flow througha flow sensor (e.g., flow sensor subsystem 30 in FIG. 2) on the exhaleline. The end of the first portion of the exhale cycle may be determinedeither by the second bellows reaching a predetermined volume, or by theflow sensor on the exhale line detecting a pre-determined low level offlow, such as no flow, or by the pressure sensor reaching a presetminimum value (PEEP). When any of these end-of-exhale conditions isreached, the control system closes the third valve and opens the fourthvalve, initiating a second portion of the exhale cycle. In the secondportion of the exhale cycle, gas in the second bellows is emittedthrough an exit port (e.g., exit port 25 in FIG. 2) to the atmosphere,thereby completing the exhale cycle. The second, third and/or fourthvalves may also be configured to variably adjust the flow of gas througheach of the valves. After the exhale cycle is complete, there mayinclude a delay (e.g., of 1 second or less and up to 3 seconds or more)before repeating the inhale cycle, as described above.

In some embodiments, a method for using a ventilator system (e.g.,ventilator system shown in FIGS. 1-2 and 15-16) includes the followingsteps. In a pressure control mode of operation, the ventilator systemuses the PIP, as determined by a preset value of a peekpressure-limiting subsystem (e.g., pressure-limiting andpressure-detection subsystem 11 in FIG. 1), to control the system. Inthis mode, both valves on the inhale line (e.g., valves 5 and 9 inFIG. 1) are opened simultaneously at the start of an inhale cycle. Thelungs of the patient inflate to a pressure that stops increasing due tothe action of the pressure-limiting subsystem. When the limitingpressure is reached, the control system receives a signal frompressure-limiting subsystem (e.g., indicating that a PIP has reached athreshold value, e.g., about 30 cmH₂O, about 40 cmH₂O, or from 15 cmH₂Oto 45 cmH₂O, or from less than 15 cmH₂O to more than 45 cmH₂O), and thecontrol system closes one or both valves on the inhale line. The exhalecycle is then initiated as described in the method above with respect tothe tidal volume inhalation control mode (e.g., with suitable delays).As above, the end of the exhale cycle may be determined via a flowsensor on the exhale line, or the second bellows volume. After theexhale cycle is complete, there may include a delay (e.g., of 1 secondor less and up to 3 seconds or more) before repeating the inhale cycledescribed above. The valves of the systems operating in the above modemay also be configured to variably adjust the flow of gas through eachof the valves.

The preceding two modes of operation are commonly referred to as“Mandatory Breathing” mode. Another clinically desirable mode iscommonly referred to as “Triggered” or “Spontaneous” breathing mode. Ina triggered breathing mode, at the end of an exhale cycle, with thesecond inhale valve closed and the first inhale valve open, pressuresensor subsystem on the inhale line may be monitored for a negativepressure (e.g., about negative 2 cmH₂O, or from negative 4 cmH₂O tonegative 2 cmH₂O, or from less than negative 4 cmH₂O to more thannegative 2 cmH₂O), and a negative pressure threshold may be set to apredetermined value. When the negative pressure threshold in pressuresensor subsystem on the inhale line is reached or the pressure ispressure sensor subsystem on the inhale line more negative than thethreshold, then the control system may open the second valve on theinhale line. The pressure-limiting subsystem on the inhale line may beset to a predetermined value (e.g., about 10 cmH₂O, or from 4 cmH₂O to20 cmH₂O, or from less than 4 cmH₂O to more than 20 cmH₂O), such thatthe breathing is assisted by a background pressure above atmosphericpressure. The end of the inhale cycle in this triggered breathing modemay be determined by the flow sensor subsystem on the inhale linedetecting a preset low level of flow (e.g., about 3 liters per minute(lpm), or from 1 lpm to 10 lpm). In this mode, the exhale cycle may bethe same as in the method described above for the mandatory breathingmodes, and the exhale cycle end may be determined by volume exhaled orby flow rate. Additionally, after the exhale cycle is complete, theremay include a delay (e.g., of 1 second or less and up to 3 seconds ormore) before repeating the inhale cycle for the triggered breathing mode(as described above). The valves of the systems operating in the abovemode may also be configured to variably adjust the flow of gas througheach of the valves.

In some embodiments, a method of detecting a flowing gas using soundincludes the following steps. A gas (or gaseous mixture including a gasand other matter, such as solid and/or liquid particles) flows through atube, where the tube can be any shape (e.g., the tube may have anapproximately cylindrical volume, a volume with an approximately squareor rectangular cross-section, a volume with a semicircularcross-section, or any other geometry). The gas generates sound as itflows through the tube. The sound is detected by a microphone that ispositioned either inside of the tube or outside of the tube. Theintensity and/or frequency of the sound is processed to convert theintensity and/or frequency of the sound into a gas flow rate.

In some cases of the method described above, the tube contains one ormore regions (e.g., diaphragms) that are configured to generate sound.The microphone may be positioned to detect the sound from the diaphragm.In some cases, a cone or other structure may be used to focus (and insome cases amplify) the sound from the regions of the tube onto themicrophone.

In some cases of the method described above, the temperature of theflowing gas may also be measured, and the intensity and/or frequency ofthe sound, and the temperature of the flowing gas, is processed toconvert the intensity and/or frequency of the sound, and the temperatureof the flowing gas, into a gas flow rate.

In some cases of the method above, the tube may contain one or moresound-generating structures (e.g., as shown in FIG. 29, or 266 a-e asshown in FIGS. 33A-33C).

In some cases of the method above, two or more microphones may be usedto detect the sound from the tube and/or the sound-generatingstructures.

In some cases of the method above, sound-generating structures andmicrophones may be configured to determine a flow direction of theflowing gas within the tube.

In some cases of the above method, insulation may be arranged toinsulate the tube and/or the microphone from ambient noise (i.e., soundsthat are not generated by the flowing gas).

In some cases of the method above, the frequency spectrum of the soundis analyzed (e.g., by a processor of the control system) and convertedinto a gas flow rate (e.g., as described above with respect to FIG. 30).For example, one or more sound-generating structures (e.g., an orifice,a whistle, a reed, or other sound-generating structure) maypreferentially generate a range of frequencies when gas flows past (orover, or through) the sound-generating structure, and the frequencyspectrum of the generated sound can be analyzed to determine theintensity of the sound within that frequency range. Such a method mayadvantageously increase the signal-to-noise ratio of the measurement.

Embodiments of the disclosed invention have been referenced in detail,and one or more examples of the disclosed invention have also beenillustrated in the accompanying figures. Each of the embodiments andexamples herein have been provided to explain the present technology,not as limitations of the present technology. Furthermore, whileparticular embodiments of the invention have been described in detail,it will be appreciated that alterations to, variations of, andequivalents to these embodiments may be readily conceived of by thoseskilled in the art, upon attaining an understanding of the foregoing.For instance, features illustrated or described with respect to oneembodiment may be used with another embodiment to yield an additionalembodiment. It is intended that the present subject matter covers allsuch modifications and variations within the scope of the appendedclaims and their equivalents. Those of ordinary skill in the art maypractice these and other modifications and variations to the presentinvention without departing from the scope of the present invention,which is more particularly set forth in the appended claims.Furthermore, the foregoing description is by way of example only, and isnot intended to limit the invention, as will be appreciated by those ofordinary skill in the art.

What is claimed is:
 1. A ventilator system, comprising: a removableairway comprising: an air inlet port; a patient inhalation port; an airexhaust port; and a patient exhalation port; and a base unit comprisingtwo pinch valves, wherein the removable airway is configured such thatair enters the removable airway through the air inlet port, wherein theremovable airway is configured such that air is exhausted from theremovable airway through the air exhaust port, wherein the removableairway is configured such that air leaves the removable airway throughthe patient inhalation port, wherein the removable airway is configuredsuch that air enters the removable airway through the patient exhalationport, wherein the removable airway does not comprise any openings otherthan the air inlet port, the air exhaust port, the patient inhalationport, and the patient exhalation port, and wherein the removable airwayis configured such that air within the removable airway does not contactany part of the base unit.
 2. The ventilator system of claim 1, whereinthe removable airway is configured such that the air entering theremovable airway through the patient exhalation port passes through theremovable airway, without contacting the base unit, and is expelledthrough the air exhaust port.
 3. The ventilator system of claim 2,wherein the removable airway and the base unit are configured such thatthe air expelled through the air exhaust port into the atmospherecontacts the base unit.
 4. The ventilator system of claim 1, wherein theremovable airway is configured such that air that enters the patientexhalation port is contained within the removable airway along acontiguous path and at no point does the contiguous path contact thebase unit.
 5. The ventilator system of claim 1, wherein the removableairway is configured such that air that passes through the removableairway has no pathway, connection, or contact to the base unit.
 6. Theventilator system of claim 1, wherein each pinch valve is configured tovariably adjust a flow of gas through the removable airway.
 7. Theventilator system of claim 6, wherein each pinch valve comprises a firstmoveable element configured to compress a tube of the removable airwaythereby restricting flow through the tube.
 8. The ventilator system ofclaim 7, wherein the first moveable element comprises a roller coupledto a rotatable arm.
 9. The ventilator system of claim 7, wherein one orboth pinch valves further comprise a fixed element, wherein the tube ispositioned between the first movable element and the fixed element, andwherein the first moveable element is configured to move towards thefixed element and compress the tube.
 10. The ventilator system of claim7, wherein one or both pinch valves further comprise a second moveableelement, wherein the first and the second moveable elements oppose eachother, wherein the tube is in between the first and the second moveableelements, and wherein the first and the second moveable elements areconfigured to move towards each other and compress the tube.
 11. Theventilator system of claim 10, wherein the first moveable elementcomprises a first roller coupled to a first rotatable arm, and whereinthe second moveable element comprises a second roller coupled to asecond rotatable arm.
 12. The ventilator system of claim 1, furthercomprising a pressure sensor and a flow sensor, wherein the removableairway comprises at least a portion of the pressure sensor and at leasta portion of the flow sensor.
 13. The ventilator system of claim 1,wherein the removable airway further comprises: a pressure sensor; aflow sensor; and first connectors for the pressure sensor and the flowsensor that mate to second connectors on the base unit.
 14. A ventilatorsystem, comprising: a removable airway comprising: an air inlet port; apatient inhalation port; an air exhaust port; and a patient exhalationport; and a base unit comprising two pinch valves; wherein the removableairway is configured such that air enters the removable airway throughthe air inlet port, wherein the removable airway is configured such thatair is exhausted from the removable airway through the air exhaust port,wherein the removable airway is configured such that air leaves theremovable airway through the patient inhalation port, wherein theremovable airway is configured such that air enters the removable airwaythrough the patient exhalation port, and wherein the removable airway isconfigured such that air that enters the patient exhalation port iscontained within the removable airway along a contiguous path and at nopoint does the contiguous path contact the base unit.
 15. The ventilatorsystem of claim 14, wherein the removable airway is configured such thatthe air entering the removable airway through the patient exhalationport passes through the removable airway, without contacting the baseunit, and is expelled through the air exhaust port.
 16. The ventilatorsystem of claim 15, wherein the removable airway and the base unit areconfigured such that the air expelled through the air exhaust port intothe atmosphere contacts the base unit.
 17. The ventilator system ofclaim 14, wherein each pinch valve is configured to variably adjust aflow of gas through the removable airway.
 18. The ventilator system ofclaim 17, wherein each pinch valve comprises a first moveable elementconfigured to compress a tube of the removable airway therebyrestricting flow through the tube.
 19. The ventilator system of claim18, wherein the first moveable element comprises a roller coupled to arotatable arm.
 20. The ventilator system of claim 18, wherein one orboth pinch valves further comprise a fixed element, wherein the tube ispositioned between the first movable element and the fixed element, andwherein the first moveable element is configured to move towards thefixed element and compress the tube.
 21. The ventilator system of claim18, wherein one or both pinch valves further comprise a second moveableelement, wherein the first and the second moveable elements oppose eachother, wherein the tube is in between the first and the second moveableelements, and wherein the first and the second moveable elements areconfigured to move towards each other and compress the tube.
 22. Theventilator system of claim 21, wherein the first moveable elementcomprises a first roller coupled to a first rotatable arm, and whereinthe second moveable element comprises a second roller coupled to asecond rotatable arm.
 23. The ventilator system of claim 14, furthercomprising a pressure sensor and a flow sensor, wherein the removableairway comprises at least a portion of the pressure sensor and at leasta portion of the flow sensor.
 24. The ventilator system of claim 14,wherein the removable airway further comprises: a pressure sensor; aflow sensor; and first connectors for the pressure sensor and the flowsensor that mate to second connectors on the base unit.